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Specific interactions between the Candida albicans ABC transporter Cdr1p ectodomain and a d ‐octapeptide derivative inhibitor
Author(s) -
Niimi Kyoko,
Harding David R. K.,
Holmes Ann R.,
Lamping Erwin,
Niimi Masakazu,
Tyndall Joel D. A.,
Can Richard D.,
Monk Brian C.
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2012.08140.x
Subject(s) - biology , candida albicans , atp binding cassette transporter , mutant , transmembrane domain , transporter , corpus albicans , rhodamine 123 , saccharomyces cerevisiae , permease , biochemistry , azole , yeast , microbiology and biotechnology , drug resistance , gene , multiple drug resistance , antifungal
Summary Overexpression of the Candida albicans ATP‐binding cassette transporter CaCdr1p causes clinically significant resistance to azole drugs including fluconazole (FLC). Screening of a ∼ 1.89 × 10 6 member d ‐octapeptide combinatorial library that concentrates library members at the yeast cell surface identified RC21v3, a 4‐methoxy‐2,3,6‐trimethylbenzenesulphonyl derivative of the d ‐octapeptide d ‐NH 2 ‐FFKWQRRR‐CONH 2 , as a potent and stereospecific inhibitor of CaCdr1p. RC21v3 chemosensitized Saccharomyces cerevisiae strains overexpressing CaCdr1p but not other fungal ABC transporters, the C. albicans MFS transporter CaMdr1p or the azole target enzyme CaErg11p, to FLC. RC21v3 also chemosensitized clinical C. albicans isolates overexpressing CaCDR1 to FLC, even when CaCDR2 was overexpressed. Specific targeting of CaCdr1p by RC21v3 was confirmed by spontaneous RC21v3 chemosensitization‐resistant suppressor mutants of S. cerevisiae expressing CaCdr1p. The suppressor mutations introduced a positive charge beside, or within, extracellular loops 1, 3, 4 and 6 of CaCdr1p or an aromatic residue near the extracytoplasmic end of transmembrane segment 5. The mutations did not affect CaCdr1p localization or CaCdr1p ATPase activity but some increased susceptibility to the CaCdr1p substrates FLC, rhodamine 6G, rhodamine 123 and cycloheximide. The suppressor mutations showed that the drug‐like CaCdr1p inhibitors FK506, enniatin, milbemycin α11 and milbemycin β9 have modes of action similar to RC21v3.