RT Journal Article
SR Electronic
T1 Crystal structures of bacterial Small Multidrug Resistance transporter EmrE in complex with structurally diverse substrates
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2022.01.11.475788
DO 10.1101/2022.01.11.475788
A1 Ali A. Kermani
A1 Olive E. Burata
A1 B. Ben Koff
A1 Akiko Koide
A1 Shohei Koide
A1 Randy B. Stockbridge
YR 2022
UL http://biorxiv.org/content/early/2022/01/11/2022.01.11.475788.abstract
AB Proteins from the bacterial small multidrug resistance (SMR) family are proton-coupled exporters of diverse antiseptics and antimicrobials, including polyaromatic cations and quaternary ammonium compounds. The transport mechanism of the Escherichia coli transporter, EmrE, has been studied extensively, but a lack of high-resolution structural information has impeded a structural description of its molecular mechanism. Here we apply a novel approach, multipurpose crystallization chaperones, to solve several structures of EmrE, including a 2.9 Å structure at low pH without substrate. We report five additional structures in complex with structurally diverse transported substrates, including quaternary phosphonium, quaternary ammonium, and planar polyaromatic compounds. These structures show that binding site tryptophan and glutamate residues adopt different rotamers to conform to disparate structures without requiring major rearrangements of the backbone structure. Structural and functional comparison to Gdx-Clo, an SMR protein that transports a much narrower spectrum of substrates, suggests that in EmrE, a relatively sparse hydrogen bond network among binding site residues permits increased sidechain flexibility.Competing Interest StatementA.K. and S.K. are listed as inventors for patents (US9512199 B2 and related patents and applications) covering aspects of the monobody technology filed by the University of Chicago and Novartis. S.K. is a scientific advisory board member and holds equity in and receives consulting fees from Black Diamond Therapeutics; receives research funding from Puretech Health and Argenx BVBA. A.A.K., O.E.B., B.B.K., and R.B.S. declare no competing interests.