title: The signaling interface of the yeast multidrug transporter Pdr5 adopts a cis conformation, and there are functional overlap and equivalence of the deviant and canonical Q-loop residues.
abstract: ABC transporters are polytopic proteins. ATP hydrolysis and substrate transport take place in separate domains, and these activities must be coordinated through a signal interface. We previously characterized a mutation (S558Y) in the yeast multidrug transporter Pdr5 that uncouples ATP hydrolysis and drug transport. To characterize the transmission interface, we used a genetic screen to isolate second-site mutations of S558Y that restore drug transport. We recovered suppressors that restore drug resistance; their locations provide functional evidence for an interface in the cis rather than the trans configuration indicated by structural and cross-linking studies of bacterial and eukaryotic efflux transporters. One mutation, E244G, defines the Q-loop of the deviant portion of NBD1, which is the hallmark of this group of fungal transporters. When moved to an otherwise wild-type background, this mutation and its counterpart in the canonical ATP-binding site Q951G show a similar reduction in drug resistance and in the very high basal-level ATP hydrolysis characteristic of Pdr5. A double E244G, Q951G mutant is considerably more drug sensitive than either of the single mutations. Surprisingly, then, the deviant and canonical Q-loop residues are functionally overlapping and equivalent in a strikingly asymmetric ABC transporter.
authors.affiliation: Department of Biology, The Catholic University of America, Washington, DC 20064, USA.
authors.forename: Neeti
authors.initials: N
authors.lastname: Ananthaswamy
authors.forename: Robert
authors.initials: R
authors.lastname: Rutledge
authors.forename: Zuben E
authors.initials: ZE
authors.lastname: Sauna
authors.forename: Suresh V
authors.initials: SV
authors.lastname: Ambudkar
authors.forename: Elliot
authors.initials: E
authors.lastname: Dine
authors.forename: Emily
authors.initials: E
authors.lastname: Nelson
authors.forename: Di
authors.initials: D
authors.lastname: Xia
authors.forename: John
authors.initials: J
authors.lastname: Golin
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D001692:Biological Transport / Q000235:genetics; D056890:Eukaryota / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D008968:Molecular Conformation; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics
chemical_list: D018528:ATP-Binding Cassette Transporters; C092438:PDR5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins