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

详细信息    查看全文

• 作者：Neeti Ananthaswamy ; Robert Rutledge ; Zuben E. Sauna ; Suresh V. Ambudkar ; Elliot Dine ; Emily Nelson ; Di Xia ; John Golin
• 刊名：Biochemistry
• 出版年：2010
• 出版时间：June 1, 2010
• 年：2010
• 卷：49
• 期：21
• 页码：4440-4449
• 全文大小：969K
• 年卷期：v.49,no.21(June 1, 2010)
• ISSN：1520-4995

文摘

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.