Name: small-scale plasma membrane preparation for the analysis of candida albicans cdr1-mgfphis
Uploaded: 2021-06-13T15:00:00
Description: Watch this Scientific Journal Video about Small-Scale Plasma Membrane Preparation for the Analysis of Candida albicans Cdr1-mGFPHis at JoVE.com

The authors gratefully acknowledge funding from the New Zealand Marsden Fund (Grant UOO1305), and a block grant from Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand (M. Niimi). They wish to thank the University of Otago for providing G. Madani with a PhD Scholarship. The authors also wish to express their gratitude to Professor Stefan Raunser and his colleagues, Dr Amir Apelbaum, and Dr Deivanayagabarathy Vinayagam, for their support and supervision during a 6-month visit of G. Madani at the Max Planck Institute of Molecular Physiology (MPIMP), Dortmund, Germany. The authors also thank the German Academic Exchange Service (DAAD) for providing G. Madani with a research grant (57381332) to visit the MPIMP.

1. Preparation of fresh or frozen stocks of transformation competent AD&#916; and AD&#916;&#916; cells
<ol>
	<li>Inoculate 25 mL of 2x YPCD [i.e., 2x YPD; 2% (w/v) yeast extract, 2% (w/v) peptone, 4% (w/v) dextrose), 0.079 % (w/v) CSM (complete supplement mixture)]35 medium with a single yeast colony and incubate overnight (o/n) for 16 h at 30 &#176;C with shaking at 200 revolutions per minute (rpm).</li>
	<li>Inoculate 225 mL of 2x YPCD medium with the 25 mL&#160;o/n culture and check the cell ...

Despite recent progress in the structural analysis of membrane proteins, no 3D structure for Cdr1, or any other PDR transporter, is currently available. So, gaining knowledge of the Cdr1 structure and its biochemical features is important, as this will not only provide insight into rational design of novel drugs to overcome efflux-mediated drug resistance, but also into the mechanism of function of an important subfamily of ABC proteins.
One of the main requirements for the structural characte...

The extraction of integral membrane proteins from their native lipid environment can dramatically affect their structure and function1,2,3,4. The complex lipid composition of biological membranes5 ensures that critically important protein-lipid interactions can occur6. Lipids maintain the structural integrity of membrane proteins, thus enabling them to function correctly in their membrane compartment destination(s)7,8. Therefore, a critical first step in the membrane protein purification is the extraction of the protein from its native environment without affecting its structure and/or function.
There are many obstacles to characterizing the structure of membrane proteins, most of which are related to their hydrophobic nature, and the difficulties of expressing properly folded and functional membrane proteins in the quantities required for X-ray crystallography or cryo-electron microscopy (cryo-EM)9,10,11,12. There are three types of membrane protein expression systems: homologous9, heterologous13,14,15, and in vitro expression systems16,17. The often-low expression levels, or the prohibitive costs, of many expression systems leave only a few hosts as the preferred option to produce membrane proteins. They include the bacterial host, Escherichia coli, the yeasts S. cerevisiae and Pichia pastoris, and higher eukaryotes such as Sf9 insect cells or mammalian cell lines18. All membrane protein expression technologies have advantages and disadvantages; however, S. cerevisiae is perhaps the best studied eukaryotic model organism suitable for membrane protein production. It is highly versatile with applications in genetic engineering, drug discovery, synthetic biology, and the expression of eukaryotic membrane proteins14,19,20,21.
In this study, a patented S. cerevisiae membrane protein expression technology21 was used, with S. cerevisiae AD&#916;14 and AD&#916;&#916;22 as the preferred hosts (Figure 1A), to overexpress and study the major C. albicans multidrug efflux pump Cdr1. Both the S. cerevisiae strains are derivatives of AD1-8u-&#160;23 that have either the ura3 (AD&#916;) or both the ura3 and his1 (AD&#916;&#916;) genes deleted to eliminate any false positive uracil or histidine prototroph transformants arising through the unwanted integration at the URA3 or the HIS1 genomic loci. The deletion of the 7 major multidrug efflux pumps23, indicated in Figure 1A, makes AD&#916;&#916; exquisitely sensitive to most xenobiotics. The gain-of-function mutant transcription factor Pdr1-3 causes the constitutive overexpression of heterologous membrane proteins such as Cdr1 (red octagons in Figure 1A) after integration of the heterologous-ORF-containing transformation cassette (Figure 1A) at the genomic PDR5 locus (blue rectangle in Figure 1A) via two homologous recombination events. Proper plasma membrane localization of C-terminally mGFPHis tagged proteins can be confirmed by confocal microscopy (Figure 1A), and the His tag can be used for nickel-affinity purification of the tagged protein. Cloning some fungal ABC transporters (e.g., Candida krusei ABC1) into pABC3-derived plasmids was, however, not possible because they could not be propagated&#160;in Escherichia coli due to cell toxicity. This prompted the development of the one-step cloning of membrane proteins14,24 tagged at either their N- or C-terminus with various affinity, epitope, or reporter tags directly into S. cerevisiae AD&#916;&#916; (Figure 1C). S. cerevisiae AD&#916;&#916; strains overexpressing various CDR1 mutants can also be created efficiently this way by using up to five individual PCR fragments that overlap by 25 bp (Figure 1C). Employing this protocol, many ORFs of interest can be cloned, expressed, and characterized at low cost and at high efficiency within a very short time span. The transformation efficiency reduces only ~2-fold with each additional PCR fragment.
If desired, expression levels can also be readily manipulated by primer design to predictably tune expression levels down to anywhere between 0.1%-50% of the usually high, constitutive expression levels25. The optimized, multifunctional, pABC314 derivative cloning vector, pABC3-XLmGFPHis26 (Figure 1B) contains a HRV-3C protease cleavage site (X; LEVLFQ|GP), a protease that performs better at 4 &#176;C than the frequently used tobacco etch virus (TEV) protease27. L is a five amino acid (GSGGS) linker, mGFP is a monomeric mutant (A206K)28,29 version of the yeast enhanced green-fluorescence protein variant yEGFP330, and His is a three amino acid linker (GGS) followed by the six-histidine (HHHHHH) nickel-affinity protein purification tag.
This expression technology has been successfully used in drug discovery and the study of membrane proteins. The first structure for a fungal azole drug target, S. cerevisiae Erg1131, was solved using this technology. It also enabled the detailed characterization of C. albicans Cdr132,33,34 and the creation of a cysteine-deficient Cdr1 molecule35 suitable for cysteine-crosslinking studies to verify any future high-resolution structure. Many other ABC transporters from major human fungal pathogens&#160;(i.e., C. albicans, Candida glabrata, Candida auris, Candida krusei, Candida utilis, Cryptococcus neoformans, Aspergillus fumigatus, Penicillium marneffei, and the Fusarium solani species complex) have also been studied in detail using this expression platform24,36,37,38,39. This has enabled the generation of a panel of S. cerevisiae strains overexpressing efflux pumps that has been used in high-throughput screens to discover the novel fluorescent efflux pump substrate Nile red40 and specific41 and broad-spectrum14,33,42,43,44&#160;efflux pump inhibitors. The use of this system also enabled the discovery of clorgyline as the first of its kind broad-spectrum fungal multidrug efflux pump inhibitor42.
Complete solubilization of membrane proteins and the creation of a homogeneous membrane protein-micelle preparation devoid of endogenous lipids, requires high detergent concentrations45. But unfortunately, this also often inactivates the membrane protein5,8,45,46. The properties of detergent monomers and their aggregation in solution are affected by the physical properties of the hydrophobic tail, the length and branching of the alkyl chain, the presence of an aromatic nucleus or fluoroalkyl side chain, or the number of polyoxyethylene units. Thus, detergent screening is an important first step to determine the most suitable detergent for membrane protein solubilization and purification.
C. albicans is a major human fungal pathogen of immunocompromised individuals that can cause serious, life threatening invasive infections47, and it can become resistant to azole antifungal drugs48,49. One of the main mechanisms of C. albicans multidrug resistance is the overexpression of Cdr150, which is a type II ATP-binding cassette (ABC) transporter51 of the ABCG subfamily located in the plasma membrane. Full-size fungal ABCG transporters (consisting of two nucleotide binding domains [NBDs] and two transmembrane domains [TMDs]) are more commonly known as pleiotropic drug resistance (PDR) transporters and are characterized by their unique inverted domain topology [NBD-TMD]2. PDR transporters are only found in plants52,53 and fungi54. Despite their importance, there are no structures for PDR transporters, although structures for human half-size ABCG transporters have recently been solved which helped create the first tentative model for Cdr133. Our recent experimental evidence suggests, however, that this model is flawed possibly because fungal PDR transporters have characteristic asymmetric NBDs resulting quite possibly in a unique transport mechanism. A high-resolution structure of Cdr1 is, therefore, required for both the rational design of novel efflux pump inhibitors that may help overcome efflux-mediated drug resistance, and to provide insights into the mechanism of action of this important ABC transporter family.
The objective of this study was to develop reliable protocols for the expression, solubilization, and purification of Cdr1 in the genetically modified S. cerevisiae expression host, with the ultimate aim of obtaining a high-resolution structure for Cdr1. As part of this process, a protease-cleavable mGFPHis double tag (Figure 1B) was designed with a 16-residue linker separating the tag from the C-terminus of Cdr1, which improved binding of the attached 6x His affinity tag to the nickel-affinity resin and enabled the monitoring of Cdr1 expression levels in living cells and during the entire purification process. A reproducible protocol for small-scale yeast plasma membrane protein preparations containing about 10% C. albicans Cdr1 (as estimated by Coomassie staining after SDS-PAGE) was also developed, which could be used for the biochemical characterization of Cdr1.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2-(N-Morpholino)ethane-sulphonic acid (MES)</td>
			<td>Sigma-Aldrich</td>
			<td>M3671</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Amino-2-(hydroxymethyl)-1,3-propanediol (Tris base; ultra-pure)</td>
			<td>Merck</td>
			<td>77-86-1</td>
			<td></td>
		</tr>
		<tr>
			<td>2,2-Didecylpropane-1,3-bis-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>NG310S</td>
			<td>LMNG</td>
		</tr>
		<tr>
			<td>2,2-Dihexylpropane-1,3-bis-&#946;-D-glucopyranoside</td>
			<td>Anatrace</td>
			<td>NG311S</td>
			<td>OGNG (MNG-OG)</td>
		</tr>
		<tr>
			<td>2,2-Dioctylpropane-1,3-bis-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>NG322S</td>
			<td>DMNG</td>
		</tr>
		<tr>
			<td>4-Trans-(4-trans-propylcyclohexyl)-cyclohexyl &#945;-D-maltopyranoside</td>
			<td>Glycon Biochemicals GmbH</td>
			<td>D99019-C</td>
			<td>PCC-&#945;-M</td>
		</tr>
		<tr>
			<td>40% Acrylamide/Bis-acrylamide (37.5:1)</td>
			<td>Bio-Rad</td>
			<td>1610148</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid (glacial)</td>
			<td>Merck</td>
			<td>64-19-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>Formedium</td>
			<td>&#160;009002-18-0</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium molybdate</td>
			<td>Sigma-Aldrich</td>
			<td>13106-76-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium persulphate (APS)</td>
			<td>Bio-Rad</td>
			<td>1610700</td>
			<td></td>
		</tr>
		<tr>
			<td>ATP disodium salt</td>
			<td>sigma-Aldrich</td>
			<td>A-6419</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromophenol blue</td>
			<td>SERVA Electrophoresis GmbH</td>
			<td>34725-61-6</td>
			<td></td>
		</tr>
		<tr>
			<td>CHAPS</td>
			<td>Anatrace</td>
			<td>C316S</td>
			<td></td>
		</tr>
		<tr>
			<td>CHAPSO</td>
			<td>Anatrace</td>
			<td>C317S</td>
			<td></td>
		</tr>
		<tr>
			<td>CSM</td>
			<td>Formedium</td>
			<td>DCS0019</td>
			<td></td>
		</tr>
		<tr>
			<td>CSM minus uracil</td>
			<td>Formedium</td>
			<td>DCS0161</td>
			<td></td>
		</tr>
		<tr>
			<td>Cyclohexyl-1-butyl-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>C324S</td>
			<td>CYMAL-4</td>
		</tr>
		<tr>
			<td>Cyclohexyl-1-heptyl-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>C327S</td>
			<td>CYMAL-7</td>
		</tr>
		<tr>
			<td>Cyclohexyl-methyl-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>C321S</td>
			<td>CYMAL-1</td>
		</tr>
		<tr>
			<td>Digitonin</td>
			<td>Sigma-Aldrich</td>
			<td>11024-24-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Dithiothreitol (DTT)</td>
			<td>Roche Diagnostics</td>
			<td>10197785103</td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Merck</td>
			<td>67-68-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Merck</td>
			<td>459836</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylenediaminetetraacetic acid disodium salt (EDTA; Titriplex III)</td>
			<td>Merck</td>
			<td>6381-92-6</td>
			<td></td>
		</tr>
		<tr>
			<td>ExoSAP-IT PCR Product Cleanup Reagent</td>
			<td>Applied Biosystems</td>
			<td>78205</td>
			<td>A blend of exonuclease and phosphatase</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Formedium</td>
			<td>50-99-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Merck</td>
			<td>56-81-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Merck</td>
			<td>G8898</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Formedium</td>
			<td>7365-45-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>Merck</td>
			<td>1003172510</td>
			<td></td>
		</tr>
		<tr>
			<td>KOD Fx Neo</td>
			<td>TOYOBO Co</td>
			<td>KFX-201</td>
			<td>Use for reliable colony PCR</td>
		</tr>
		<tr>
			<td>lithium acetate (LiAc)</td>
			<td>Sigma-Aldrich</td>
			<td>546-89-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium chloride hexa-hydrate</td>
			<td>sigma-Aldrich</td>
			<td>M2393</td>
			<td></td>
		</tr>
		<tr>
			<td>MES</td>
			<td>Formedium</td>
			<td>145224-94-8</td>
			<td></td>
		</tr>
		<tr>
			<td>n-Decanoyl-N-hydroxyethyl-glucamide</td>
			<td>Anatrace</td>
			<td>H110S</td>
			<td>HEGA-10</td>
		</tr>
		<tr>
			<td>n-Decanoyl-N-methyl-glucamide</td>
			<td>Anatrace</td>
			<td>M320S</td>
			<td>MEGA-10</td>
		</tr>
		<tr>
			<td>n-Decyl-phosphocholine</td>
			<td>Anatrace</td>
			<td>F304S</td>
			<td>Fos-choline-10</td>
		</tr>
		<tr>
			<td>n-Decyl-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>D322S</td>
			<td>DM</td>
		</tr>
		<tr>
			<td>n-Dodecyl-N,N-dimethyl-3-ammonio-1-propanesulphonate</td>
			<td>Anatrace</td>
			<td>AZ312S</td>
			<td>Anzergent 3-12</td>
		</tr>
		<tr>
			<td>n-Dodecyl-N,N-dimethylamine-N-oxide</td>
			<td>Anatrace</td>
			<td>D360S</td>
			<td>LDAO</td>
		</tr>
		<tr>
			<td>n-Dodecyl-&#945;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>D310HA</td>
			<td>&#945;-DDM</td>
		</tr>
		<tr>
			<td>n-Dodecyl-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>D310S</td>
			<td>&#946;-DDM</td>
		</tr>
		<tr>
			<td>n-Nonyl-&#946;-D-glucopyranoside</td>
			<td>Anatrace</td>
			<td>N324S</td>
			<td>NG</td>
		</tr>
		<tr>
			<td>n-Nonyl-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>N330S</td>
			<td>NM</td>
		</tr>
		<tr>
			<td>n-Octadecyl-N,N-dimethyl-3-ammonio-1-propanesulphonate</td>
			<td>Anatrace</td>
			<td>AZ318S</td>
			<td>Anzergent 3-18</td>
		</tr>
		<tr>
			<td>n-Octyl-N,N-dimethyl-3-ammonio-1-propanesulphonate</td>
			<td>Anatrace</td>
			<td>AZ308S</td>
			<td>Anzergent 3-8</td>
		</tr>
		<tr>
			<td>n-Octyl-phosphocholine</td>
			<td>Anatrace</td>
			<td>F300S</td>
			<td>Fos-choline-8</td>
		</tr>
		<tr>
			<td>n-Octyl-&#946;-D-glucopyranoside</td>
			<td>Anatrace</td>
			<td>O311S</td>
			<td>OG</td>
		</tr>
		<tr>
			<td>n-Tetradecyl-phosphocholine</td>
			<td>Anatrace</td>
			<td>F312S</td>
			<td>Fos-choline-14</td>
		</tr>
		<tr>
			<td>n-Tetradecyl-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>T315S</td>
			<td>TDM</td>
		</tr>
		<tr>
			<td>n-Tridecyl-phosphocholine</td>
			<td>Anatrace</td>
			<td>F310S</td>
			<td>Fos-choline-13</td>
		</tr>
		<tr>
			<td>n-Tridecyl-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>T323S</td>
			<td>-</td>
		</tr>
		<tr>
			<td>n-Undecyl-&#946;-D-maltopyranoside</td>
			<td>Anatrace</td>
			<td>U300S</td>
			<td>UM (UDM)</td>
		</tr>
		<tr>
			<td>N,N,N&#8217;,N&#8217;-tetramethyl-ethylenediamine (TEMED)</td>
			<td>Sigma-Aldrich</td>
			<td>T9281</td>
			<td></td>
		</tr>
		<tr>
			<td>Octylphenoxypolyethoxyethanol</td>
			<td>Sigma-Aldrich</td>
			<td>9002-93-1</td>
			<td>TRITON X-100</td>
		</tr>
		<tr>
			<td>Oligomycin</td>
			<td>Sigma-Aldrich</td>
			<td>75351</td>
			<td></td>
		</tr>
		<tr>
			<td>Peptone</td>
			<td>Formedium</td>
			<td>3049-73-7</td>
			<td></td>
		</tr>
		<tr>
			<td>phenylmethylsulfonyl fluoride (PMSF)</td>
			<td>Roche Diagnostics</td>
			<td>329-98-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Phusion&#160;Hot Start Flex DNA Polymerase</td>
			<td>New England Biolabs</td>
			<td>M0535S</td>
			<td>High-fidelity DNA polymerase</td>
		</tr>
		<tr>
			<td>polyethylene glycol (PEG 3350)</td>
			<td>Sigma-Aldrich</td>
			<td>25322-68-3</td>
			<td></td>
		</tr>
		<tr>
			<td>polyoxyethylenesorbitan monooleate</td>
			<td>Sigma-Aldrich</td>
			<td>9005-65-6</td>
			<td>TWEEN 80</td>
		</tr>
		<tr>
			<td>Potassium nitrate</td>
			<td>Sigma-Aldrich</td>
			<td>P8394</td>
			<td></td>
		</tr>
		<tr>
			<td>Protein Assay Kit</td>
			<td>Bio-Rad</td>
			<td>5000122</td>
			<td>RC DC Protein Assay Kit II</td>
		</tr>
		<tr>
			<td>QC Colloidal Coomassie Stain</td>
			<td>Bio-Rad</td>
			<td>1610803</td>
			<td></td>
		</tr>
		<tr>
			<td>Prism Ultra Protein Ladder (10-245 kDa)</td>
			<td>Abcam</td>
			<td>AB116028</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium azide</td>
			<td>Sigma-Aldrich</td>
			<td>71289</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium dodecyl sulphate</td>
			<td>Sigma-Aldrich</td>
			<td>151-21-3</td>
			<td>SDS</td>
		</tr>
		<tr>
			<td>Sodium L-ascorbate BioXtra</td>
			<td>Sigma-Aldrich</td>
			<td>11140</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose Monododecanoate</td>
			<td>Anatrace</td>
			<td>S350S</td>
			<td>DDS</td>
		</tr>
		<tr>
			<td>Sulphuric acid</td>
			<td>Sigma-Aldrich</td>
			<td>339741</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast extract</td>
			<td>Formedium</td>
			<td>008013-01-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast nitrogen base without amino acids</td>
			<td>Formedium</td>
			<td>CYN0402</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;Equipment (type)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge&#160; (Eppendorf 5804)</td>
			<td>Eppendorf</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge (Beckman Ultra)</td>
			<td>Beckman</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge (Sorvall RC6)</td>
			<td>Sorvall</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>FSEC apparatus (NGC Chromatography Medium Pressure system equipped with a fluorescence detector, an autosampler, a fractionator)</td>
			<td>Bio-Rad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gel imaging (GelDoc EZ Imager)</td>
			<td>Bio-Rad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate reader (Synergy 2 Multi-Detection)</td>
			<td>BioTek Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PCR thermal cycler (C1000 Touch)</td>
			<td>Bio-Rad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Power supply (PowerPac)</td>
			<td>Bio-Rad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SDS PAGE (Mini-PROTEAN Tetra)</td>
			<td>Bio-Rad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Shaking incubator (Multitron)</td>
			<td>Infors HT, Bottmingen</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Superose 6 Increase 10/300 GL</td>
			<td>GE Healthcare Life Sciences</td>
			<td>GE17-5172-01</td>
			<td></td>
		</tr>
		<tr>
			<td>UV/Visible spectrophotometer (Ultraspec 6300 pro)</td>
			<td colspan="2">Amersham BioSciences UK Ltd</td>
			<td></td>
		</tr>
	</tbody>
</table>

small-scale plasma membrane preparation for the analysis of candida albicans cdr1-mgfphis

The successful biochemical and biophysical characterization of ABC transporters depends heavily on the choice of the heterologous expression system. Over the past two decades, we have developed a yeast membrane protein expression platform that has been used to study many important fungal membrane proteins. The expression host Saccharomyces cerevisiae AD&#916;&#916; is deleted in seven major endogenous ABC transporters and it contains the transcription factor Pdr1-3 with a gain-of-function mutation that enables the constitutive overexpression of heterologous membrane protein genes stably integrated as single copies at the genomic PDR5 locus. The creation of versatile plasmid vectors and the optimization of one-step cloning strategies enables the rapid and accurate cloning, mutagenesis, and expression of heterologous ABC transporters. Here, we describe the development and use of a novel protease-cleavable mGFPHis double tag (i.e., the monomeric yeast enhanced green fluorescent protein yEGFP3 fused to a six-histidine affinity purification tag) that was designed to avoid possible interference of the tag with the protein of interest and to increase the binding efficiency of the His tag to nickel-affinity resins. The fusion of mGFPHis to the membrane protein ORF (open reading frame) enables easy quantification of the protein by inspection of polyacrylamide gels and detection of degradation products retaining the mGFPHis tag. We demonstrate how this feature facilitates detergent screening for membrane protein solubilization. A protocol for the efficient, fast, and reliable isolation of the small-scale plasma membrane preparations of the C-terminally tagged Candida albicans multidrug efflux transporter Cdr1 overexpressed in S. cerevisiae AD&#916;&#916;, is presented. This small-scale plasma membrane isolation protocol generates high-quality plasma membranes within a single working day. The plasma membrane preparations can be used to determine the enzyme activities of Cdr1 and Cdr1 mutant variants.

A high frequency of transformation of S. cerevisiae AD&#916;&#916; (~4 x 104 transformants/&#181;g) was achieved with pYES2 (Figure 2B). As expected, the no DNA (i.e., ddH2O only) control gave no transformants, and 1 &#181;g of the linear CDR1-mGFPHis transformation cassette (Figure 1A) gave ~50 transformants (Figure 2C)&#160;with the optimized AD&#916;&#916; transformation protocol. ...

Watch this Scientific Journal Video about Small-Scale Plasma Membrane Preparation for the Analysis of Candida albicans Cdr1-mGFPHis at JoVE.com

Small-Scale Plasma Membrane Preparation for the Analysis of Candida albicans Cdr1-mGFPHis

This article presents a small-scale plasma membrane isolation protocol for the characterization of Candida albicans ABC (ATP-binding cassette) protein Cdr1, overexpressed in Saccharomyces cerevisiae. A protease-cleavable C-terminal mGFPHis double tag with a 16-residue linker between Cdr1 and the tag was designed to facilitate the purification and detergent-screening of Cdr1.

Small-Scale Plasma Membrane Preparation for the Analysis of Candida albicans Cdr1-mGFPHis

The successful biochemical and biophysical characterization of ABC transporters depends heavily on the choice of the heterologous expression system. Over ...

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