Name: a modified yeast-one hybrid system for heteromeric protein complex-dna interaction studies
Uploaded: 2017-07-24T15:00:00
Description: Watch this Scientific Journal Video about A Modified Yeast-one Hybrid System for Heteromeric Protein Complex-DNA Interaction Studies at JoVE.com

We thank S.S. Wang, M. Amar and A. Galla for critical reading of the manuscript. Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under award numbers RO1GM067837 and RO1GM056006 (to S.A.K). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

1. Construct and Reporter Plasmid Preparation
<ol>
	<li>PCR amplify the promoter regions / &#34;fragments&#34; (preferably ~250 - 500 bp) of the target DNA to be analyzed for further cloning into the entry vector using E. coli (TOP10).</li>
	<li>Upon sequencing confirmation, subclone the positive clone in a compatible pGLacZi expression vector 7 as previously described 8,9,10,<sup cl...

<ol>
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The existing Y1H standard procedure is suitable for identifying a single protein prey binding to its DNA bait. With various technical modifications, the existing system has been harnessed for defining transcriptional regulatory networks. However, TFs are known to function as a part of complexes involving two or more TFs or proteins, with only some of the TF capable of binding to the DNA. Proteins or TFs which possess only the protein-binding domains and lack the ability to bind to DNA are more likely to work in a complex...

In general, to understand protein-DNA interactions, the Y1H assay is the preferred system successfully used in a laboratory setting 1. The basic Y1H assay involves two components: a) a reporter construct with DNA of interest successfully cloned upstream of a gene encoding a reporter protein; and b) an expression construct which will generate a fusion protein between the TF of interest and a yeast transcription activation domain (AD). The DNA of interest is commonly referred to as &#39;bait&#39; while the fusion protein is known as &#39;prey&#39;. In past years, multiple versions of the Y1H assay have been developed to suit specific needs with their own advantages 2. The existing Y1H assay can be successfully implemented to identify and validate interaction of one protein at a time with its DNA bait, but lacks the capability to identify heterodimeric or multimeric protein-DNA interactions.
The method described here is a modified version of the existing Y1H enabling researchers to simultaneously study multiple proteins binding to their target DNA sequence(s). The goal of this assay is to express the protein of interest with an activation domain (pDEST22: TF) and evaluate the activation of the candidate DNA regions fused to a reporter in the presence and/or absence of the interacting protein partner (pDEST32&#916;DBD-TF) in the yeast system. This assay will allow us to determine whether the interaction between these two proteins is required for the activation of the target. This is a GATEWAY cloning compatible system and therefore feasible to use in a regular laboratory setting. Thisprotocol is based on direct transformation, which provides the ease of co-transformation of different TFs in a yeast system. Thus, it is an advantageous strategy to validate the protein complexes binding to their possible DNA targets for in vitro molecular and functional validation for any system. Current techniques such as Tandem affinity purification (TAP) methods are costly and labor intensive but allow detection of protein hetrocomplexes on a large scale 3,4,5. This modified yeast one-hybrid can be successfully performed in a regular lab setting on a small scale (Figure 1) and is also cost effective. The Y1.5H assay can facilitate researchers across the community to test and validate their hypothesis towards defining the role of multimeric protein complex binding to a common DNA target using a heterologous system. Based on the findings, the hypothesis could be validated in vivo in the preferred system of study. Recently, we have used this approach to define the role of a TF and its mode of action to regulate flowering in Arabidopsis 6.

<table border="0" cellpadding="0" cellspacing="0" width="846">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">pDEST22 vector</td>
			<td style="width:132px;">Invitrogen</td>
			<td style="width:157px;">PQ1000101</td>
			<td style="width:332px;">Pro-Quest Two hybrid system kit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">pDEST32delatDBD</td>
			<td style="width:132px;">Invitrogen</td>
			<td style="width:157px;">PQ1000102</td>
			<td>Pro-Quest Two hybrid system kit; this vecor is modified. It is pDEST32 minus DNA binding Domain</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">pENTR/D-TOPO Cloning Kit</td>
			<td style="width:132px;">Invitrogen</td>
			<td style="width:157px;">K240020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">YM4271 Strain</td>
			<td style="width:132px;">Clontech</td>
			<td style="width:157px;">K1603-1</td>
			<td>MATCHMAKER One-Hybrid System</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">pEXP-AD502</td>
			<td style="width:132px;">Invitrogen</td>
			<td style="width:157px;">PQ1000101</td>
			<td>Pro-Quest Two hybrid system kit</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:225px;">GATEWAY LR Clonase II enzyme mix</td>
			<td style="width:132px;">Invitrogen</td>
			<td style="width:157px;">11791020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">YPDA media</td>
			<td style="width:132px;">Clontech</td>
			<td style="width:157px;">630410</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">SD-Agar</td>
			<td style="width:132px;">Clontech</td>
			<td style="width:157px;">630412</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">SD minimal media</td>
			<td style="width:132px;">Clontech</td>
			<td style="width:157px;">630411</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Uracil DO Supplement</td>
			<td style="width:132px;">Clontech</td>
			<td style="width:157px;">630416</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Tryptophan Do Supplement</td>
			<td style="width:132px;">Clontech</td>
			<td style="width:157px;">630413</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Tris Base</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:157px;">BP152-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">EDTA</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:157px;">S311-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">LiAc</td>
			<td style="width:132px;">Sigma-Aldrich</td>
			<td style="width:157px;">L4158</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Saplmon Sperm (10mg/ml)</td>
			<td style="width:132px;">Invitrogen</td>
			<td style="width:157px;">15632011</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">96 well round bottom Plate</td>
			<td>Greiner bio-one</td>
			<td align="right">650101</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">PEG3350</td>
			<td style="width:132px;">Sigma-Aldrich</td>
			<td style="width:157px;">1546547</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">96-deep well block</td>
			<td style="width:132px;">USA Scientific</td>
			<td style="width:157px;">1896-2000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Sealable Foil</td>
			<td style="width:132px;">USA Scientific</td>
			<td style="width:157px;">2923-0110</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Araseal</td>
			<td style="width:132px;">Excel Scientific</td>
			<td style="width:157px;">B-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">2-mercaptoethanol</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:157px;">034461-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">ONPG</td>
			<td style="width:132px;">Sigma-Aldrich</td>
			<td style="width:157px;">73660</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2CO3</td>
			<td style="width:132px;">Sigma-Aldrich</td>
			<td style="width:157px;">223484</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Na2HPO4&#160;</td>
			<td style="width:132px;">Sigma-Aldrich</td>
			<td style="width:157px;">S3264</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">NaH2PO4&#160;</td>
			<td style="width:132px;">Sigma-Aldrich</td>
			<td style="width:157px;">S3139</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">KCL</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:157px;">BP366-500</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">MgSO4&#160;</td>
			<td style="width:132px;">Sigma-Aldrich</td>
			<td style="width:157px;">83266</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">HCL</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:157px;">SA54-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Drybath</td>
			<td style="width:132px;">Thermo Fischer</td>
			<td style="width:157px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Voretx</td>
			<td style="width:132px;">Thermo Fischer</td>
			<td style="width:157px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Centrifgue</td>
			<td style="width:132px;">Eppendorf</td>
			<td style="width:157px;">Centrifuge 5810R</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Plate Reader</td>
			<td style="width:132px;">Molecular Device</td>
			<td style="width:157px;"></td>
			<td>SPECTRAMAX PLUS Microplate Spectrophotometer</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:225px;">Incubator</td>
			<td style="width:132px;">Thermo Fisher</td>
			<td style="width:157px;">Model No. 5250- 37 Degree, 6250-30 degrees</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Shaker Incubator</td>
			<td style="width:132px;">New Brunswick</td>
			<td style="width:157px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Water Bath</td>
			<td style="width:132px;">Thermo Fisher</td>
			<td style="width:157px;">IsoTemp 205</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Puncher</td>
			<td style="width:132px;"></td>
			<td style="width:157px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">50 ml Falocn</td>
			<td style="width:132px;">BD Falcon</td>
			<td style="width:157px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Beaker</td>
			<td style="width:132px;">Nalgene</td>
			<td style="width:157px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Flask</td>
			<td style="width:132px;">Nalgene</td>
			<td style="width:157px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:225px;">Petriplates (150mm)</td>
			<td style="width:132px;">Greiner bio-one</td>
			<td style="width:157px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

a modified yeast-one hybrid system for heteromeric protein complex-dna interaction studies

Over the years, the yeast one-hybrid assay has proven to be an important technique for the identification and validation of physical interactions between proteins such as transcription factors (TFs) and their DNA target. The method presented here utilizes the underlying concept of the Y1H but is modified further to study and validate protein complexes binding to their target DNA. Hence, it is referred to as the modified yeast one-hybrid (Y1.5H) assay. This assay is cost effective and can be easily performed in a regular laboratory setting. Albeit using a heterologous system, the described method could be a valuable tool to test and validate the heteromeric protein complex binding to their DNA target(s) for functional genomics in any system of study, especially plant genomics.

The general plate set-up procedure for the co-transformation of DNA regions in the yeast cells with protein of interest (Figure 2). The plate set-up can be modified according to the need of the experiment and number of DNA regions/fragments tested. After day-5 of the protocol a well-grown and positive plate should be visible as in Figure 3. In our study, the promoter region of 2600 bp upstream from the start of the transcription ...

Watch this Scientific Journal Video about A Modified Yeast-one Hybrid System for Heteromeric Protein Complex-DNA Interaction Studies at JoVE.com

A Modified Yeast-one Hybrid System for Heteromeric Protein Complex-DNA Interaction Studies

The modified yeast one-hybrid assay described here is an extension of the classical yeast one-hybrid (Y1H) assay to study and validate the heteromeric protein complex-DNA interaction in a heterologous system for any functional genomics study.

Over the years, the yeast one-hybrid assay has proven to be an important technique for the identification and validation of physical interactions between ...

The overall goal of this experiment is to study and validate the heteromeric protein complex-DNA interaction in a heterologous system for any functional genomic study in a regular laboratory setting. This method can help answer key questions in functional genomics field, such as planned genomics. The main advantage of this technique is that it detects protein DNA interactions involving more than one protein or transcription factor.Begin this procedure on the afternoon of what will be designated as day one. Start a 5 milliliter culture in synthetic defined or SD medium without uracil from a freshly streaked Petri dish. Incubate overnight in a 30 degree Celsius shaker.On the following afternoon, inoculate 10 milliliters of YPDA medium with 500 microliters of the overnight culture and incubate overnight in a 30 degree Celsius shaker. Early in the morning of the following day, inoculate 100 milliliters of YPDA medium with 2 milliliters of the overnight culture. Grow this fresh culture at 30 degrees Celsius until the optical density at 600 nanometers, reaches 0.4 to 0.8.Centrifuge at 1000 times G and 21 degrees Celsius for 5 minutes. Discard the supernatant. Add 10 milliliters of sterile water and reconstitute the pellet by vortexing.Centrifuge at 1000 times G and 21 degrees Celsius for five minutes. Discard the supernatant, add 2 milliliters of TE lithium acetate, and reconstitute the pellet by vortexing. Centrifuge at 1000 times G and 21 degrees Celsius for five minutes.Discard the supernatant. Add 4 milliliters of TE lithium acetate plus 400 microliters of salmon sperm DNA and resuspend the pellet by pipetting up and down. The cells are now ready for transformation as demonstrated in the next segment.Co-transformation of the cells is performed in a 96 well U-bottom mixing plate. First, distribute 20 microliters of competent cells per well in the 96 well plate. Then, add to the wells, 150 nanograms each of the two plasmids and the normalization control.This schematic shows the general plate set up for the co-transformation of the yeast cells with protein of interest. The plate set up can be modified according to the need of the experiment and number of DNA regions or fragments tested. Add 100 microliters of TE lithium acetate polyethylene glycol per well and mix three times by pipetting.Cover the plate with a breathable seal and incubate at 30 degrees Celsius for 20 to 30 minutes. Heat shock at 42 degrees Celsius for precisely 20 minutes. After the heat shock, centrifuge at 1000 times G and 21 degrees Celsius for 5 minutes.Use a multichannel pipette to remove the supernatant. Add 110 microliters of TE and mix. Centrifuge again for 5 minutes.Remove 100 microliters of the supernatant from each well. Immerse a puncher in 100%ethanol, flame it, wait for one minute for the puncher pins to cool, and then use the sterile puncher to resuspend the pellet. Transfer cells onto SD tryptophan and lucine drop out auger plates.Incubate the plates at 30 degrees Celsius for two days. On the afternoon of day five, retrieve the auger plates from the incubator. Fill each well of the sterile 96 well u-bottom mixing plate with 50 microliters of TE.Prewet a sterile puncher in TE, punch the colonies from the SD tryptophan and lucine drop out plate, and resuspend them in the TE filled plate.Transfer the colonies onto new SD tryptophan and lucine drop out auger plates, for optimal surface coverage. Incubate the plates at 30 degrees Celsius for 2 days. On the afternoon of day 7, retrieve the auger plates from the incubator.Fill each well of a sterile 96 well u-bottom mixing plate with 50 microliters of SD tryptophan and lucine drop out medium. Fill each well of a sterile 96 deep well block with 180 microliters of SD tryptophan and lucine drop out medium. Sterilize the puncher, prewet the puncher and medium, and transfer colonies from the plate to the wells that each contain 50 microliters of medium.Transfer 20 microliters of yeast to the 180 microliters of SD tryptophan and lucine drop out medium. Seal the block with a breathable seal, and incubate at 30 degrees Celsius with shaking for 36 hours. On the morning of day nine, transfer 100 microliters of culture to 500 microliters of YPDA medium in a sterilized 96 deep well block.Cover with a breathable seal and incubate at 30 degrees Celsius with agitation at 200 rpm for three to five hours. After three to five hours, resuspend the culture and transfer 125 microliters from each well to a spectrophotometer plate. Measure the optical density at 600 nanometers to ensure it is between 0.3 and 0.6.Centrifuge the remaining cells in the deep well block at 3000 times G and 21 degrees Celsius for 10 minutes. Remove the supernatant by inverting. Add 200 microliters of Z buffer to each well and vortex.Centrifuge at 3000 G and 21 degrees Celsius for five minutes. Remove the supernatant by inverting. Add 21 microliters of Z buffer to each well and vortex.Cover the plate with sealing foil that is resistant to freeze thaw cycles. In a fume hood, perform 4 cycles of freeze/thaw using liquid nitrogen and a 42 degree Celsius water bath. Add 200 microliters of freshly prepared Z buffer beta mercaptoethanol ONPG solution to each well.Incubate at 30 degrees Celsius for 17 to 24 hours or until color develops. On the morning of day 10, check that the color has developed. Add 110 microliters of one molar sodium carbonate to each well to stop the reaction.Record the time and vortex the plate. Centrifuge at 3000 times G and 21 degrees Celsius for ten minutes. Use a multichannel pipette to transfer 125 microliters of supernatant from each well to a spectrophotometer plate.Measure the optical density at 420 nanometers. Calculate beta galactosidase activity in a spread sheet as described in the text protocol. In this study, the promoter region of 2600 base pairs upstream from the start of the transcription start site was segmented into six regions or fragments.This photo is an example of a well-grown and positive plate after day five of the protocol. In this representative result, DNA fragments one and four show positive interaction with the protein A and B complex. Upon the measurement of beta golactisidase activity, fragment one shows four fold induction of the reporter gene activity.It is important to remember that this procedure is recommended for obtaining information on DNA regions only after the confirmation of the proposed protein protein interaction and is not designed to provide information of target sites. Following this procedures, other methods, such as chip assay and Msar can be preformed in order to answer additional questions. For example, identifying the target sites in vivo.After watching this video, you should have a good understanding of how to test and validate the role of multimeric protein complexes binding to a common DNA target.

a-modified-yeast-one-hybrid-system-for-heteromeric-protein-complex

Research

JoVE Journal

Biochemistry

Method for Identifying Small Molecule Inhibitors of the Protein-protein Interaction Between HCN1 and TRIP8b

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed ubiquitously throughout the brain, where they function to regulate the excitability of neurons. The subcellular distribution of these channels in pyramidal neurons of hippocampal area CA1 is regulated by tetratricopeptide repeat-containing Rab8b interacting protein (TRIP8b), an auxiliary subunit. Genetic knockout of HCN pore forming subunits or TRIP8b, both lead to an increase in antidepressant-like behavior, suggesting that limiting the function of HCN channels may be useful as a treatment for Major Depressive Disorder (MDD). Despite significant therapeutic interest, HCN channels are also expressed in the heart, where they regulate rhythmicity. To circumvent off-target issues associated with blocking cardiac HCN channels, our lab has recently proposed targeting the protein-protein interaction between HCN and TRIP8b in order to specifically disrupt HCN channel function in the brain. TRIP8b binds to HCN pore forming subunits at two distinct interaction sites, although here the focus is on the interaction between the tetratricopeptide repeat (TPR) domains of TRIP8b and the C terminal tail of HCN1. In this protocol, an expanded description of a method for purifying TRIP8b and executing a high throughput screen to identify small molecule inhibitors of the interaction between HCN and TRIP8b, is described. The method for high throughput screening utilizes a Fluorescence Polarization (FP) -based assay to monitor the binding of a large TRIP8b fragment to a fluorophore-tagged eleven amino acid peptide corresponding to the HCN1 C terminal tail. This method allows &#39;hit&#39; compounds to be identified based on the change in the polarization of emitted light. Validation assays are then performed to ensure that &#39;hit&#39; compounds are not artifactual.

The interaction between HCN channels and their auxiliary subunit has been identified as a therapeutic target in Major Depressive Disorder. Here, a fluorescence polarization-based method for identifying small molecule inhibitors of this protein-protein interaction, is presented.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed ubiquitously throughout the brain, where they function to regulate the ...

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating these studies, reincorporation of detergent-solubilized membrane proteins into liposomes is a stochastic process where protein topology is impossible to enforce. This paper offers an alternative method to these challenging techniques that utilizes a liposome-based scaffold. Protein solubility is enhanced by deletion of the transmembrane domain, and these amino acids are replaced with a tethering moiety, such as a His-tag. This tether interacts with an anchoring group (Ni2+ coordinated by nitrilotriacetic acid (NTA(Ni2+)) for His-tagged proteins), which enforces a uniform protein topology at the surface of the liposome. An example is presented wherein the interaction between Dynamin-related protein 1 (Drp1) with an integral membrane protein, Mitochondrial Fission Factor (Mff), was investigated using this scaffold liposome method. In this work, we have demonstrated the ability of Mff to efficiently recruit soluble Drp1 to the surface of liposomes, which stimulated its GTPase activity. Moreover, Drp1 was able to tubulate the Mff-decorated lipid template in the presence of specific lipids. This example demonstrates the effectiveness of scaffold liposomes using structural and functional assays and highlights the role of Mff in regulating Drp1 activity.

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

This paper describes a method for assessing the interactions and assemblies of integral membrane proteins in vitro with various partner factors in a lipid-proximal environment.

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating ...

Recombinant Protein Expression, Crystallization, and Biophysical Studies of a Bacillus-conserved Nucleotide Pyrophosphorylase, BcMazG

To overcome safety restrictions and regulations when studying genes and proteins from true pathogens, their homologues can be studied. Bacillus anthracis is an obligate pathogen that causes fatal inhalational anthrax. Bacillus cereus is considered a useful model for studying B. anthracis due to its close evolutionary relationship. The gene cluster ba1554 - ba1558 of B. anthracis is highly conserved with the bc1531- bc1535 cluster in B. cereus, as well as with the bt1364-bt1368 cluster in Bacillus thuringiensis, indicating the critical role of the associated genes in the Bacillus genus. This manuscript describes methods to prepare and characterize a protein product of the first gene (ba1554) from the gene cluster in B. anthracis using a recombinant protein of its ortholog in B. cereus, bc1531.

Recombinant Protein Expression, Crystallization, and Biophysical Studies of a Bacillus-conserved Nucleotide Pyrophosphorylase, BcMazG

Bacillus anthracis is the obligate pathogen of fatal inhalational anthrax, so studies of its genes and proteins are strictly regulated. An alternative approach is to study orthologous genes. We describe biophysicochemical studies of a B. anthracis ortholog in B. cereus, bc1531, requiring minimal experimental equipment and lacking serious safety concerns.

To overcome safety restrictions and regulations when studying genes and proteins from true pathogens, their homologues can be studied. Bacillus anthracis ...

A Yeast 2-Hybrid Screen in Batch to Compare Protein Interactions

Screening for protein-protein interactions using the yeast 2-hybrid assay has long been an effective tool, but its use has largely been limited to the discovery of high-affinity interactors that are highly enriched in the library of interacting candidates. In a traditional format, the yeast 2-hybrid assay can yield too many colonies to analyze when conducted at low stringency where low affinity interactors might be found. Moreover, without a comprehensive and complete interrogation of the same library against different bait plasmids, a comparative analysis cannot be achieved. Although some of these problems can be addressed using arrayed prey libraries, the cost and infrastructure required to operate such screens can be prohibitive. As an alternative, we have adapted the yeast 2-hybrid assay to simultaneously uncover dozens of transient and static protein interactions within a single screen utilizing a strategy termed DEEPN (Dynamic Enrichment for Evaluation of Protein Networks), which incorporates high-throughput DNA sequencing and computation to follow the evolution of a population of plasmids that encode interacting partners. Here, we describe customized reagents and protocols that allow a DEEPN screen to be executed easily and cost-effectively.

Batch processing of yeast 2-hybrid screens allows for direct comparison of the interaction profiles of multiple bait proteins with a highly complex set of prey fusion proteins. Here, we describe refined methods, new reagents, and how to implement their use for such screens.

Screening for protein-protein interactions using the yeast 2-hybrid assay has long been an effective tool, but its use has largely been limited to the ...

Application of Biolayer Interferometry (BLI) for Studying Protein-Protein Interactions in Transcription

A transcription factor&#160;(TF) is a protein that regulates gene expression by interacting with the RNA polymerase, another TF, and/or template DNA. GrgA is a novel transcription activator found specifically in the obligate intracellular bacterial pathogen Chlamydia. Protein pulldown assays using affinity beads have revealed that GrgA binds two &#963; factors, namely &#963;66 and &#963;28, which recognize different sets of promoters for genes whose products are differentially required at developmental stages. We have used BLI to confirm and further characterize the interactions. BLI demonstrates several advantages over pulldown: 1) It reveals real-time association and dissociation between binding partners, 2) It generates quantitative kinetic parameters, and 3) It can detect bindings that pulldown assays often fail to detect. These characteristics have enabled us to deduce the physiological roles of GrgA in gene expression regulation in Chlamydia, and possible detailed interaction mechanisms. We envision that this relatively affordable technology can be extremely useful for studying transcription and other biological processes.

Application of Biolayer Interferometry BLI for Studying Protein-Protein Interactions in Transcription

Interactions of transcription factors (TFs) with the RNA polymerase are usually studied using pulldown assays. We apply a Biolayer Interferometry (BLI) technology to characterize the interaction of GrgA with the chlamydial RNA polymerase. Compared to pulldown assays, BLI detects real-time association and dissociation, offers higher sensitivity, and is highly quantitative.

A transcription factor&#160;(TF) is a protein that regulates gene expression by interacting with the RNA polymerase, another TF, and/or template DNA. GrgA ...

Quantification of Protein Interaction Network Dynamics using Multiplexed Co-Immunoprecipitation

Dynamic protein-protein interactions control cellular behavior, from motility to DNA replication to signal transduction. However, monitoring dynamic interactions among multiple proteins in a protein interaction network is technically difficult. Here, we present a protocol for Quantitative Multiplex Immunoprecipitation (QMI), which allows quantitative assessment of fold changes in protein interactions based on relative fluorescence measurements of Proteins in Shared Complexes detected by Exposed Surface epitopes (PiSCES). In QMI, protein complexes from cell lysates are immunoprecipitated onto microspheres, and then probed with a labeled antibody for a different protein in order to quantify the abundance of PiSCES. Immunoprecipitation antibodies are conjugated to different MagBead spectral regions, which allows a flow cytometer to differentiate multiple parallel immunoprecipitations and simultaneously quantify the amount of probe antibody associated with each. QMI does not require genetic tagging and can be performed using minimal biomaterial compared to other immunoprecipitation methods. QMI can be adapted for any defined group of interacting proteins, and has thus far been used to characterize signaling networks in T cells and neuronal glutamate synapses. Results have led to new hypothesis generation with potential diagnostic and therapeutic applications. This protocol includes instructions to perform QMI, from the initial antibody panel selection through to running assays and analyzing data. The initial assembly of a QMI assay involves screening antibodies to generate a panel, and empirically determining an appropriate lysis buffer. The subsequent reagent preparation includes covalently coupling immunoprecipitation antibodies to MagBeads, and biotinylating probe antibodies so they can be labeled by a streptavidin-conjugated fluorophore. To run the assay, lysate is mixed with MagBeads overnight, and then beads are divided and incubated with different probe antibodies, and then a fluorophore label, and read by flow cytometry. Two statistical tests are performed to identify PiSCES that differ significantly between experimental conditions, and results are visualized using heatmaps or node-edge diagrams.

Quantitative Multiplex Immunoprecipitation (QMI) uses flow cytometry for sensitive detection of differences in the abundance of targeted protein-protein interactions between two samples. QMI can be performed using a small amount of biomaterial, does not require genetically engineered tags, and can be adapted for any previously defined protein interaction network.

Dynamic protein-protein interactions control cellular behavior, from motility to DNA replication to signal transduction. However, monitoring dynamic ...

Creating Highly Specific Chemically Induced Protein Dimerization Systems by Stepwise Phage Selection of a Combinatorial Single-Domain Antibody Library

Protein dimerization events that occur only in the presence of a small-molecule ligand enable the development of small-molecule biosensors for the dissection and manipulation of biological pathways. Currently, only a limited number of chemically induced dimerization (CID) systems exist and engineering new ones with desired sensitivity and selectivity for specific small-molecule ligands remains a challenge in the field of protein engineering. We here describe a high throughput screening method, combinatorial binders-enabled selection of CID (COMBINES-CID), for the de novo engineering of CID systems applicable to a large variety of ligands. This method uses the two-step selection of a phage-displayed combinatorial nanobody library to obtain 1) &#34;anchor binders&#34; that first bind to a ligand of interest and then 2) &#34;dimerization binders&#34; that only bind to anchor binder-ligand complexes. To select anchor binders, a combinatorial library of over 109 complementarity-determining region (CDR)-randomized nanobodies is screened with a biotinylated ligand and hits are validated with the unlabeled ligand by bio-layer interferometry (BLI). To obtain dimerization binders, the nanobody library is screened with anchor binder-ligand complexes as targets for positive screening and the unbound anchor binders for negative screening. COMBINES-CID is broadly applicable to select CID binders with other immunoglobulin, non-immunoglobulin, or computationally designed scaffolds to create biosensors for in vitro and in vivo detection of drugs, metabolites, signaling molecules, etc.

Creating chemically induced protein dimerization systems with desired affinity and specificity for any given small molecule ligand would have many biological sensing and actuation applications. Here, we describe an efficient, generalizable method for de novo engineering of chemically induced dimerization systems via the stepwise selection of a phage-displayed combinatorial single-domain antibody library.

Protein dimerization events that occur only in the presence of a small-molecule ligand enable the development of small-molecule biosensors for the ...

Monitoring Protein-RNA Interaction Dynamics In Vivo at High Temporal Resolution Using &#967;CRAC

The interaction between RNA-binding proteins (RBPs) and their RNA substrates exhibits fluidity and complexity. Within its lifespan, a single RNA can be bound by many different RBPs that will regulate its production, stability, activity, and degradation. As such, much has been done to understand the dynamics that exist between these two types of molecules. A particularly important breakthrough came with the emergence of &#8216;cross-linking and immunoprecipitation&#8217; (CLIP). This technique allowed stringent investigation into which RNAs are bound by a particular RBP. In short, the protein of interest is UV cross-linked to its RNA substrates in vivo, purified under highly stringent conditions, and then the RNAs covalently cross-linked to the protein are converted into cDNA libraries and sequenced. Since its conception, many derivative techniques have been developed in order to make CLIP amenable to particular fields of study. However, cross-linking using ultraviolet light is notoriously inefficient. This results in extended exposure times that make the temporal study of RBP-RNA interactions impossible. To overcome this issue, we recently designed and built much-improved UV irradiation and cell harvesting devices. Using these new tools, we developed a protocol for time-resolved analyses of RBP-RNA interactions in living cells at high temporal resolution: Kinetic CRoss-linking and Analysis of cDNAs (&#967;CRAC). We recently used this technique to study the role of yeast RBPs in nutrient stress adaptation. This manuscript provides a detailed overview of the &#967;CRAC method and presents recent results obtained with the Nrd1 RBP.

Kinetic cross-linking and analysis of cDNA is a method that allows investigation of the dynamics of protein-RNA interactions in living cells at high temporal resolution. Here the protocol is described in detail, including the growth of yeast cells, UV cross-linking, harvesting, protein purification, and next generation sequencing library preparation steps.

The interaction between RNA-binding proteins (RBPs) and their RNA substrates exhibits fluidity and complexity. Within its lifespan, a single RNA can be ...

Native Cell Membrane Nanoparticles System for Membrane Protein-Protein Interaction Analysis

Protein-protein interactions in cell membrane systems play crucial roles in a wide range of biological processes- from cell-to-cell interactions to signal transduction; from sensing environmental signals to biological response; from metabolic regulation to developmental control. Accurate structural information of protein-protein interactions is crucial for understanding the molecular mechanisms of membrane protein complexes and for the design of highly specific molecules to modulate these proteins. Many in vivo and in vitro approaches have been developed for the detection and analysis of protein-protein interactions. Among them the structural biology approach is unique in that it can provide direct structural information of protein-protein interactions at the atomic level. However, current membrane protein structural biology is still largely limited to detergent-based methods. The major drawback of detergent-based methods is that they often dissociate or denature membrane protein complexes once their native lipid bilayer environment is removed by detergent molecules. We have been developing a&#160;native cell membrane nanoparticle system for membrane protein structural biology. Here, we demonstrate the use of this system in the analysis of protein-protein interactions on the cell membrane with a case study of the oligomeric state of AcrB.

Presented here is a protocol for the determination of oligomeric state of membrane proteins that utilizes a native cell membrane nanoparticle system in conjunction with electron microscopy.

Protein-protein interactions in cell membrane systems play crucial roles in a wide range of biological processes- from cell-to-cell interactions to signal ...

An Economical and Versatile High-Throughput Protein Purification System Using a Multi-Column Plate Adapter

Protein purification is imperative to the study of protein structure and function and is usually used in combination with biophysical techniques. It is also a key component in the development of new therapeutics. The evolving era of functional proteomics is fueling the demand for high-throughput protein purification and improved techniques to facilitate this. It was hypothesized that a multi column plate adaptor (MCPA) can interface multiple chromatography columns of different resins with multi-well plates for parallel purification. This method offers an economical and versatile method of protein purification that can be used under gravity or vacuum, rivaling the speed of an automated system. The MCPA can be used to recover milligram yields of protein by an affordable and time efficient method for subsequent characterization and analysis. The MCPA has been used for high-throughput affinity purification of SH3 domains. Ion exchange has also been demonstrated via the MCPA to purify protein post Ni-NTA affinity chromatography, indicating how this system can be adapted to other purification types. Due to its setup with multiple columns, individual customization of parameters can be made in the same purification, unachievable by the current plate-based methods.

A multi-column plate adapter allows chromatography columns to be interfaced with multi-well collection plates for parallel affinity or ion exchange purification providing an economical high throughput protein purification method. It can be used under gravity or vacuum yielding milligram quantities of protein via affordable instrumentation.

Protein purification is imperative to the study of protein structure and function and is usually used in combination with biophysical techniques. It is ...