title: A key structural domain of the Candida albicans Mdr1 protein.
abstract: A major multidrug transporter, MDR1 (multidrug resistance 1), a member of the MFS (major facilitator superfamily), invariably contributes to an increased efflux of commonly used azoles and thus corroborates their direct involvement in MDR in Candida albicans. The Mdr1 protein has two transmembrane domains, each comprising six transmembrane helices, interconnected with extracellular loops and ICLs (intracellular loops). The introduction of deletions and insertions through mutagenesis was used to address the role of the largest interdomain ICL3 of the MDR1 protein. Most of the progressive deletants, when overexpressed, eliminated the drug resistance. Notably, restoration of the length of the ICL3 by insertional mutagenesis did not restore the functionality of the protein. Interestingly, most of the insertion and deletion variants of ICL3 became amenable to trypsinization, yielding peptide fragments. The homology model of the Mdr1 protein showed that the molecular surface-charge distribution was perturbed in most of the ICL3 mutant variants. Taken together, these results provide the first evidence that the CCL (central cytoplasmic loop) of the fungal MFS transporter of the DHA1 (drug/proton antiporter) family is critical for the function of MDR. Unlike other homologous proteins, ICL3 has no apparent role in imparting substrate specificity or in the recruitment of the transporter protein.
authors.affiliation: Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Ajeet
authors.initials: A
authors.lastname: Mandal
authors.forename: Antresh
authors.initials: A
authors.lastname: Kumar
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Singh
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Lynn
authors.forename: Khyati
authors.initials: K
authors.lastname: Kapoor
authors.forename: Rajendra
authors.initials: R
authors.lastname: Prasad
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D002176:Candida albicans / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D025141:Drug Resistance, Fungal / Q000235:genetics / Q000502:physiology; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017931:DNA Primers; D005656:Fungal Proteins; D011994:Recombinant Proteins