We thank the staff at the beamlines 19ID, 24ID, and 13ID at Advanced Photon Source, Lemont, IL, for support during data collection on various crystals. We are grateful to Dmitry Lyumkis, Salk Institute for fetching us the low resolution cryo-EM map at early stages of EM map/model building, which was used to build the initial IKK1 molecular replacement search model. The research leading to these results has received funding from NIH grants AI064326, CA141722, and GM071862 to GG. SP is currently a Wellcome Trust DBT India Intermediate Fellow.

<ol>
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The authors declare no competing financial interests or other conflicts of interest.

Production, crystallization and structure solution of two related IKK proteins 
We set out to determine the X-ray crystal structure of IKK1/&#945; with the notion that it would be a relatively straightforward exercise given our experience with IKK2/&#946; protein production, crystallization, and structure determination. However, we were highly surprised that these two related proteins behaved very differently regarding the ease of crystallization. Despite efforts from several high-profile laboratori...

Transcriptional activities of the NF-&#954;B family of dimeric transcription factors are required for diverse cellular functions ranging from inflammation and immunity to survival and death. These activities are stringently controlled in cells and a loss of regulation leads to various pathological conditions, including autoimmune disorders, and cancer1,2,3. In the absence of a stimulus, the activities of NF-&#954;B are kept inhibited by I&#954;B (Inhibitor of -&#954;B) proteins4. The phosphorylation of specific Ser residues on I&#954;B proteins marks them for ubiquitination and subsequent proteasomal degradation or selective processing5. Two highly homologous Ser/Thr kinases, IKK2/&#946; and IKK1/&#945;, act as central regulators of NF-&#954;B activities by carrying out these phosphorylation events6,7.
Interactions between a ligand and a receptor transduces a signal through a series of mediators leading to the activation of NF-&#954;B factors. The NF-&#954;B signalling process can broadly be classified into two distinct pathways &#8211; canonical and non-canonical (alternative)8. The activity of IKK2/&#946; primarily regulates the NF-&#954;B signalling of the canonical pathway that is essential for inflammatory and innate immune responses9. A distinct feature of this pathway is a rapid and short-lived activation of IKK2/&#946;10 within a hitherto biochemically uncharacterized IKK complex &#8212; presumed to be composed of IKK1 and IKK2, as well as a regulatory component, NEMO (NF-&#954;B Essential Modulator)11,12,13. Between the two catalytic IKK subunits of the IKK complex, IKK2 is primarily responsible14 for the phosphorylation of specific residues of prototypical I&#954;Bs (&#945;, -&#946;, &#38; -&#947;) bound to NF-&#954;B, and also an atypical I&#954;B protein, NF-&#954;B1/p105, which is a precursor of the NF-&#954;B p50 subunit5. Phosphorylation induced ubiquitination and proteasomal degradation of I&#954;B (or processing of p105) leads to the release and activation of a specific set of NF-&#954;B dimers15. Aberrant NF-&#954;B activity due to mis-regulated function of IKK2 has been observed in many cancers as well as in autoimmune disorders2,3,16.
In contrast to IKK2/&#946;, activity of IKK1/&#945; regulates NF-&#954;B signalling of the non-canonical pathway, which is essential for development and immunity. IKK1 phosphorylates specific residues of NF-&#954;B2/p100 on its C-terminal I&#954;B&#948; segment, which leads to its processing and the generation of p52. The formation of transcriptionally active p52:RelB heterodimer initiates a slow and sustained response to developmental signals7,17,18,19,20. Interestingly, the generation of the central NF-&#954;B factor p52 of this pathway is critically dependent on another factor, NF-&#954;B Inducing Kinase (NIK)21,22, but not on IKK2 or NEMO. In resting cells, the level of NIK remains low due to its constant proteasome-dependent degradation23,24,25. Upon stimulation of cells by &#39;non-canonical&#39; ligands, and in certain malignant cells, NIK becomes stabilized to recruit and activate IKK1/&#945;. Kinase activities of both NIK and IKK1 are essential for efficient processing of p100 into p527. IKK1 and NIK phosphorylate three serines (Ser866, 870 and 872) of NF-&#954;B2/p100 on its C-terminal I&#954;B&#948; segment leading to its processing and the generation of p52. Aberrant activation of the non-canonical pathway has been implicated in many malignancies including multiple myeloma26,27,28.
Several highly efficient and specific inhibitors for IKK2/&#946; are known, although none so far have turned out to be an effective drug. In contrast, IKK1/&#945;-specific inhibitors are sparse. This may stem partly from our lack of structural and biochemical information on IKK1/&#945;, which limits our understanding of the mechanistic basis of activation of NF-&#954;B by IKK1 in cells, and rational drug design. The X-ray structures of IKK2/&#946; provided us with insights into the activation mechanism of IKK2/&#946;29; however, these structures could not reveal how different upstream stimuli trigger activation of IKK1/&#945; or IKK2/&#946; to regulate distinct sets of NF-&#954;B activities 30,31. To understand the mechanistic basis underlying the distinct signalling function of IKK1/&#945;, and to establish a platform for rational drug design, we focused on determining the structure of IKK1/&#945;.

<table>
	<tbody>
		<tr>
			<td>Cellfectin/Cellfectin II</td>
			<td>Thermo Fisher Scientific</td>
			<td>10362100</td>
			<td>Cellfectin is now discontinued, replaced by Cellfectin II</td>
		</tr>
		<tr>
			<td>Sf900 III Insect cell medium</td>
			<td>Thermo Fisher Scientific</td>
			<td>12658-027</td>
			<td></td>
		</tr>
		<tr>
			<td>SF9 cells</td>
			<td>Thermo Fisher Scientific</td>
			<td>12659017</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-IKK1 antibody</td>
			<td>Novus Biologicals</td>
			<td>NB100-56704</td>
			<td>Previously sold by Imgenex</td>
		</tr>
		<tr>
			<td>anti-PentaHis antibody</td>
			<td>Qiagen</td>
			<td>34460</td>
			<td></td>
		</tr>
		<tr>
			<td>PVDF membrane</td>
			<td>Millipore</td>
			<td>IPVH00010</td>
			<td>Nitrocellulose can also be used</td>
		</tr>
		<tr>
			<td>Ni-NTA agarose</td>
			<td>Qiagen</td>
			<td>30210</td>
			<td></td>
		</tr>
		<tr>
			<td>Bradford assay reagent</td>
			<td>BioRad</td>
			<td>500001</td>
			<td></td>
		</tr>
		<tr>
			<td>Superdex 200 column</td>
			<td>GE Healthcare</td>
			<td>28989335</td>
			<td></td>
		</tr>
		<tr>
			<td>Amicon concentrator</td>
			<td>Millipore</td>
			<td>UFC801008, UFC803008, UFC201024, UFC203024</td>
			<td></td>
		</tr>
		<tr>
			<td>Compound A</td>
			<td>Bayer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Calbiochem IKK-inhibitor XII</td>
			<td>Calbiochem</td>
			<td>401491</td>
			<td></td>
		</tr>
		<tr>
			<td>Staurosporine</td>
			<td>SIGMA</td>
			<td>S4400</td>
			<td></td>
		</tr>
		<tr>
			<td>MLN120B</td>
			<td>Millenium</td>
			<td>Gift item</td>
			<td></td>
		</tr>
		<tr>
			<td>AMPPNP</td>
			<td>SIGMA</td>
			<td>A2647</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextran sulfate</td>
			<td>SIGMA</td>
			<td>51227, 42867, 31404,</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextran sulfate</td>
			<td>Alfa Aesar</td>
			<td>J62101</td>
			<td></td>
		</tr>
		<tr>
			<td>PEG</td>
			<td>SIGMA</td>
			<td>93593, 81210, 88276, 95904, 81255, 89510, 92897, 81285, 95172</td>
			<td>Some of them are new Cat # on SIGMA catalogue. What we had was originally from Fluka that had different Cat #.</td>
		</tr>
		<tr>
			<td>Crystallization Screens</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Crystal Screen I and II (Crystal Screen HT)</td>
			<td>Hampton Research</td>
			<td>HR2-130</td>
			<td></td>
		</tr>
		<tr>
			<td>Index HT</td>
			<td>Hampton Research</td>
			<td>HR2-134</td>
			<td></td>
		</tr>
		<tr>
			<td>PEG/Ion and PEG/Ion2 (PEG/Ion HT)</td>
			<td>Hampton Research</td>
			<td>HR2-139</td>
			<td></td>
		</tr>
		<tr>
			<td>PEGRX 1 and PEGRx 2 (PEGRx HT)</td>
			<td>Hampton Research</td>
			<td>HR2-086</td>
			<td></td>
		</tr>
		<tr>
			<td>SaltRx 1 and SaltRx 2 (SaltRx HT)</td>
			<td>Hampton Research</td>
			<td>HR2-136</td>
			<td></td>
		</tr>
		<tr>
			<td>Crystal mounts</td>
			<td>Hampton Research</td>
			<td>HR8-188, 190, 192, 194</td>
			<td></td>
		</tr>
		<tr>
			<td>Synchrotron</td>
			<td>The Advanced Photon Source (APS) at the U.S. Department of Energy&#8217;s Argonne National Laboratory</td>
			<td>Beamline 19 ID</td>
			<td>The Advanced Photon Source (APS) at the U.S. Department of Energy&#8217;s Argonne National Laboratory provides ultra-bright, high-energy storage ring-generated X-ray beams for research in almost all scientific disciplines.</td>
		</tr>
	</tbody>
</table>

a guide to production, crystallization, and structure determination of human ikk1/&#945;

A class of extracellular stimuli requires activation of IKK1/&#945; to induce generation of an NF-&#954;B subunit, p52, through processing of its precursor p100. p52 functions as a homodimer or heterodimer with another NF-&#954;B subunit, RelB. These dimers in turn regulate the expression of hundreds of genes involved in inflammation, cell survival, and cell cycle. IKK1/&#945; primarily remains associated with IKK2/&#946; and NEMO as a ternary complex. However, a small pool of it is also observed as a low molecular weight complex(es). It is unknown if the p100 processing activity is triggered by activation of IKK1/&#945; within the larger or the smaller complex pool. Constitutive activity of IKK1/&#945; has been detected in several cancers and inflammatory diseases. To understand the mechanism of activation of IKK1/&#945;, and enable its use as a drug target, we expressed recombinant IKK1/&#945; in different host systems, such as E. coli, insect, and mammalian cells. We succeeded in expressing soluble IKK1/&#945; in baculovirus infected insect cells, obtaining mg quantities of highly pure protein, crystallizing it in the presence of inhibitors, and determining its X-ray crystal structure. Here, we describe the detailed steps to produce the recombinant protein, its crystallization, and its X-ray crystal structure determination.

Cloning and expression of different constructs of IKK1/&#945; 
Full length human IKK1/&#945; was cloned into the baculovirus expression vector pFastBacHTa within its EcoRI and NotI restriction sites to obtain an N-terminal hexa-Histidine tagged IKK1. The tag could be removed by TEV protease digestion. Since full length IKK1/&#945; contains flexible regions on both ends, and flexible regions usually render a protein difficult to crystallize, we cloned various truncate...

Watch this Scientific Journal Video about A Guide to Production, Crystallization, and Structure Determination of Human IKK1/ÃŽÂ± at JoVE.com

A Guide to Production, Crystallization, and Structure Determination of Human IKK1/&#945;

I&#954;B Kinase 1/&#945; (IKK1/&#945; CHUK) is a Ser/Thr protein kinase that is involved in a myriad of cellular activities primarily through activation of NF-&#954;B transcription factors. Here, we describe the main steps necessary for the production and crystal structure determination of this protein.

A class of extracellular stimuli requires activation of IKK1/&#945; to induce generation of an NF-&#954;B subunit, p52, through processing of its ...

a-guide-to-production-crystallization-structure-determination-human

Research

JoVE Journal

Biochemistry

9.1K Views.  University of California, San Diego. IκB Kinase 1/α (IKK1/α CHUK) is a Ser/Thr protein kinase that is involved in a myriad of cellular activities primarily through activation of NF-κB transcription factors. Here, we describe the main steps necessary for the production and crystal structure determination of this protein.

Video: A Guide to Production, Crystallization, and Structure Determination of Human IKK1/α

Thermostabilization, Expression, Purification, and Crystallization of the Human Serotonin Transporter Bound to S-citalopram

The serotonin transporter is a sodium and chloride-coupled transporter that &#34;pumps&#34; extracellular serotonin into cells. S-citalopram is a drug used to treat depression and anxiety by binding to the serotonin transporter with high-affinity, blocking serotonin reuptake. Here we report an efficient procedure and a set of tools to stabilize, express, purify, and crystallize serotonin transporter-antibody complexes bound to S-citalopram and other antidepressants. Mutations which stabilize the serotonin transporter were identified using an S-citalopram binding assay. Serotonin transporter expressed in baculovirus-transduced HEK293S GnTI- cells, was reconstituted into proteoliposomes and used to raise high-affinity antibodies. We have developed a strategy to discover antibodies that are useful for structural studies. A straightforward approach for the expression of antibody fragments in Sf9 cells has also been established. Transporter-antibody complexes purified using this procedure are well-behaved and readily crystallize, producing complexes with S-citalopram that diffract X-rays to 3-4 &#197; resolution. The strategies developed here can be utilized to determine the structure of other challenging membrane proteins.

Thermostabilization, Expression, Purification, and Crystallization of the Human Serotonin Transporter Bound to S-citalopram

This manuscript describes how to screen for thermostabilizing mutations, purify the human serotonin transporter, generate high affinity antibodies, and crystallize the serotonin transporter-antibody complex bound to the antidepressant drug S-citalopram. This protocol can be adapted to the study of other challenging membrane transporters, receptors, and channels.

The serotonin transporter is a sodium and chloride-coupled transporter that &#34;pumps&#34; extracellular serotonin into cells. S-citalopram is a drug ...

Combining Wet and Dry Lab Techniques to Guide the Crystallization of Large Coiled-coil Containing Proteins

Obtaining crystals for structure determination can be a difficult and time consuming proposition for any protein. Coiled-coil proteins and domains are found throughout nature, however, because of their physical properties and tendency to aggregate, they are traditionally viewed as being especially difficult to crystallize. Here, we utilize a variety of quick and simple techniques designed to identify a series of possible domain boundaries for a given coiled-coil protein, and then quickly characterize the behavior of these proteins in solution. With the addition of a strongly fluorescent tag (mRuby2), protein characterization is simple and straightforward. The target protein can be readily visualized under normal lighting and can be quantified with the use of an appropriate imager. The goal is to quickly identify candidates that can be removed from the crystallization pipeline because they are unlikely to succeed, affording more time for the best candidates and fewer funds expended on proteins that do not produce crystals. This process can be iterated to incorporate information gained from initial screening efforts, can be adapted for high-throughput expression and purification procedures, and is augmented by robotic screening for crystallization.

We describe a framework incorporating straightforward biochemical and computational analysis to guide the characterization and crystallization of large coiled-coil domains. This framework can be adapted for globular proteins or extended to incorporate a variety of high-throughput techniques.

Obtaining crystals for structure determination can be a difficult and time consuming proposition for any protein. Coiled-coil proteins and domains are ...

Production, Crystallization and Structure Determination of C. difficile PPEP-1 via Microseeding and Zinc-SAD

New therapies are needed to treat Clostridium difficile infections that are a major threat to human health. The C. difficile metalloprotease PPEP-1 is a target for future development of inhibitors to decrease the virulence of the pathogen. To perform biophysical and structural characterization as well as inhibitor screening, large amounts of pure and active protein will be needed. We have developed a protocol for efficient production and purification of PPEP-1 by the use of E. coli as the expression host yielding sufficient amounts and purity of protein for crystallization and structure determination. Additionally, using microseeding, highly intergrown crystals of PPEP-1 can be grown to well-ordered crystals suitable for X-ray diffraction analysis. The methods could also be used to produce other recombinant proteins and to study the structures of other proteins producing intergrown crystals.

Production, Crystallization and Structure Determination of C. difficile PPEP-1 via Microseeding and Zinc-SAD

Proline-proline endopeptidase-1 (PPEP-1) is a secreted metalloprotease and promising drug-target from the human pathogen Clostridium difficile. Here we describe all methods necessary for the production and structure determination of this protein.

New therapies are needed to treat Clostridium difficile infections that are a major threat to human health. The C. difficile metalloprotease PPEP-1 is a ...

Laboratory Scale Production and Purification of a Therapeutic Antibody

Ensuring the successful production of a therapeutic antibody begins early on in the development process. The first stage is vector expression of the antibody genes followed by stable transfection into a suitable cell line. The stable clones are subjected to screening in order to select those clones with desired production and growth characteristics. This is a critical albeit time-consuming step in the process. This protocol considers vector selection and sourcing of antibody sequences for the expression of a therapeutic antibody. The methods describe preparation of vector DNA for stable transfection of a suspension variant of human embryonic kidney 293 (HEK-293) cell line, using polyethylenimine (PEI). The cells are transfected as adherent cells in serum-containing media to maximize transfection efficiency, and afterwards adapted to serum-free conditions. Large scale production, setup as batch overgrow cultures is used to yield antibody protein that is purified by affinity chromatography using an automated fast protein liquid chromatography (FPLC) instrument. The antibody yields produced by this method can provide sufficient protein to begin initial characterization of the antibody. This may include in vitro assay development or physicochemical characterization to aid in the time-consuming task of clonal screening for lead candidates. This method can be transferable to the development of an expression system for the production of biosimilar antibodies.

This protocol describes the production of a therapeutic antibody in a mammalian expression system. The methods described include preparation of vector DNA, stable transfection and serum-free adaptation of a human embryonic kidney 293 cell line, set up of large scale cultures and purification using affinity chromatography.

Ensuring the successful production of a therapeutic antibody begins early on in the development process. The first stage is vector expression of the ...

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 ...

High Precision FRET at Single-molecule Level for Biomolecule Structure Determination

A protocol on how to perform high-precision interdye distance measurements using F&#246;rster resonance energy transfer (FRET) at the single-molecule level in multiparameter fluorescence detection (MFD) mode is presented here. MFD maximizes the usage of all &#34;dimensions&#34; of fluorescence to reduce photophysical and experimental artifacts and allows for the measurement of interdye distance with an accuracy up to ~1 &#197; in rigid biomolecules. This method was used to identify three conformational states of the ligand-binding domain of the N-methyl-D-aspartate (NMDA) receptor to explain the activation of the receptor upon ligand binding. When comparing the known crystallographic structures with experimental measurements, they agreed within less than 3 &#197; for more dynamic biomolecules. Gathering a set of distance restraints that covers the entire dimensionality of the biomolecules would make it possible to provide a structural model of dynamic biomolecules.

A protocol for high-precision FRET experiments at the single molecule level is presented here. Additionally, this methodology can be used to identify three conformational states in the ligand-binding domain of the N-methyl-D-aspartate (NMDA) receptor. Determining precise distances is the first step towards building structural models based on FRET experiments.

A protocol on how to perform high-precision interdye distance measurements using F&#246;rster resonance energy transfer (FRET) at the single-molecule ...

Production, Crystallization, and Structure Determination of the IKK-binding Domain of NEMO

NEMO is a scaffolding protein which plays an essential role in the NF-&#954;B pathway by assembling the IKK-complex with the kinases IKK&#945; and IKK&#946;. Upon activation, the IKK complex phosphorylates the I&#954;B molecules leading to NF-&#954;B nuclear translocation and activation of target genes. Inhibition of the NEMO/IKK interaction is an attractive therapeutic paradigm for the modulation of NF-&#954;B pathway activity, making NEMO a target for inhibitors design and discovery. To facilitate the process of discovery and optimization of NEMO inhibitors, we engineered an improved construct of the IKK-binding domain of NEMO that would allow for structure determination of the protein in the apo form and while bound to small molecular weight inhibitors. Here, we present the strategy utilized for the design, expression and structural characterization of the IKK-binding domain of NEMO. The protein is expressed in E. coli cells, solubilized under denaturing conditions and purified through three chromatographic steps. We discuss the protocols for obtaining crystals for structure determination and describe data acquisition and analysis strategies. The protocols will find wide applicability to the structure determination of complexes of NEMO and small molecule inhibitors.

We describe protocols for the structure determination of the IKK-binding domain of NEMO by X-ray crystallography. The methods include protein expression, purification and characterization as well as strategies for successful crystal optimization and structure determination of the protein in its unbound form.

NEMO is a scaffolding protein which plays an essential role in the NF-&#954;B pathway by assembling the IKK-complex with the kinases IKK&#945; and ...

Analysis and Specification of Starch Granule Size Distributions

Starch from all plant sources are made up of granules in a range of sizes and shapes having different occurrence frequencies, i.e., exhibiting a size and a shape distribution. Starch granule size data determined using several types of particle sizing techniques are often problematic due to poor reproducibility or lack of statistical significance resulting from some insurmountable systematic errors, including sensitivity to granule shapes and limits of granule-sample sizes. We outlined a procedure for reproducible and statistically valid determinations of starch granule size distributions using the electrical sensing zone technique, and for specifying the determined granule lognormal size distributions using an adopted two-parameter multiplicative form with improved accuracy and comparability. It is applicable to all granule sizing analyses of gram-scale starch samples, and, therefore, could facilitate studies on how starch granule sizes are molded by the starch biosynthesis apparatus and mechanisms; and how they impact properties and functionality of starches for food and industrial uses. Representative results are presented from replicate analyses of granule size distributions of sweetpotato starch samples using the outlined procedure. We further discussed several key technical aspects of the procedure, especially, the multiplicative specification of granule lognormal size distributions and some technical means for overcoming frequent aperture blockage by granule aggregates.

Presented here is a procedure for reproducible and statistically valid determinations of starch granule size distributions, and for specifying the determined granule lognormal size distributions using a two-parameter multiplicative form. It is applicable to all granule sizing analyses of gram-scale starch samples for plant and food science research. &#160;

Starch from all plant sources are made up of granules in a range of sizes and shapes having different occurrence frequencies, i.e., exhibiting a size and ...

Crystallization and Structural Determination of an Enzyme:Substrate Complex by Serial Crystallography in a Versatile Microfluidic Chip

The preparation of well diffracting crystals and their handling before their X-ray analysis are two critical steps of biocrystallographic studies. We describe a versatile microfluidic chip that enables the production of crystals by the efficient method of counter-diffusion. The convection-free environment provided by the microfluidic channels is ideal for crystal growth and useful to diffuse a substrate into the active site of the crystalline enzyme. Here we applied this approach to the CCA-adding enzyme of the psychrophilic bacterium Planococcus halocryophilus in the presented example. After crystallization and substrate diffusion/soaking, the crystal structure of the enzyme:substrate complex was determined at room temperature by serial crystallography and the analysis of multiple crystals directly inside the chip. The whole procedure preserves the genuine diffraction properties of the samples because it requires no crystal handling.

A versatile microfluidic device is described that enables the crystallization of an enzyme using the counter-diffusion method, the introduction of a substrate in the crystals by soaking, and the 3D structure determination of the enzyme:substrate complex by a serial analysis of crystals inside the chip at room temperature.

The preparation of well diffracting crystals and their handling before their X-ray analysis are two critical steps of biocrystallographic studies. We ...

The Extraction of Liver Glycogen Molecules for Glycogen Structure Determination

Liver glycogen is a hyperbranched glucose polymer that is involved in the maintenance of blood sugar levels in animals. The properties of glycogen are influenced by its structure. Hence, a suitable extraction method that isolates representative samples of glycogen is crucial to the study of this macromolecule. Compared to other extraction methods, a method that employs a sucrose density gradient centrifugation step can minimize molecular damage. Based on this method, a recent publication describes how the density of the sucrose solution used during centrifugation was varied (30%, 50%, 72.5%) to find the most suitable concentration to extract glycogen particles of a wide variety of sizes, limiting the loss of smaller particles. A 10 min boiling step was introduced to test its ability to denature glycogen degrading enzymes, thus preserving glycogen. The lowest sucrose concentration (30%) and the addition of the boiling step were shown to extract the most representative samples of glycogen.

An optimal sucrose concentration was determined for the extraction of liver glycogen using sucrose density gradient centrifugation. The addition of a 10 min boiling step to inhibit glycogen-degrading enzymes proved beneficial.

Liver glycogen is a hyperbranched glucose polymer that is involved in the maintenance of blood sugar levels in animals. The properties of glycogen are ...