title: Alanine scanning of all cysteines and construction of a functional cysteine-less Cdr1p, a multidrug ABC transporter of Candida albicans.
abstract: Herein, we discuss the role of the native cysteines present in a major multidrug ABC transporter of Candida albicans, Cdr1p, and describe the construction of this transporter's functional cysteine-less (cysless) protein version for cross-linking studies. In the experiments in which all 23 cysteines were replaced individually, we observed that most of the cysteine replacements were tolerated by the protein, but the replacement of C1056, C1091, C1106, C1294 or C1336 resulted in an enhanced drug susceptibility together with an abrogated drug efflux. Notably, the ATPase activity was uncoupled, which largely remained unaffected in these variants. The substitution of the critical cysteines with serines restored the normal expression and functionality of Cdr1p because serine can effectively mimic the hydrogen bonding properties of cysteine. Finally, we constructed a functional cysless His-tagged Cdr1p in which all the cysteines of the native protein were replaced with alanines and the critical cysteines were replaced with serines. Notably, cysless GFP-tagged variant of Cdr1p was non-functional. The cysless His-tagged variant of Cdr1p is the first example of a cysless ABC transporter in yeast, and it will lead to a greater understanding of the architecture of this important protein and provide insight into the nature of drug binding and interdomain communication.
authors.affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi, India. rp47jnu@gmail.com
authors.forename: Rajendra
authors.initials: R
authors.lastname: Prasad
authors.forename: Abdul Haseeb
authors.initials: AH
authors.lastname: Shah
authors.forename: Hina
authors.initials: H
authors.lastname: Sanwal
authors.forename: Khyati
authors.initials: K
authors.lastname: Kapoor
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000409:Alanine / Q000737:chemistry; D019943:Amino Acid Substitution; D002176:Candida albicans / Q000187:drug effects / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D025141:Drug Resistance, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed
chemical_list: D018528:ATP-Binding Cassette Transporters; C094693:CDR1 protein, Candida albicans; D003432:Cross-Linking Reagents; D005656:Fungal Proteins; D026901:Membrane Transport Proteins; D003545:Cysteine; D000409:Alanine