The structural basis of promiscuity in small multidrug resistance transporters

• Published in: Nature communications Vol. 11; no. 1; pp. 6064 - 9
• Main Authors: Kermani, Ali A., Macdonald, Christian B., Burata, Olive E., Ben Koff, B., Koide, Akiko, Denbaum, Eric, Koide, Shohei, Stockbridge, Randy B.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 27.11.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 631/1647/1453; 631/45/612/1237; 631/535/1266; 631/57/2283; Amino Acid Sequence; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; BASIC BIOLOGICAL SCIENCES; Binding Sites; Biocides; Biological Transport; Cassettes; Cations; Crystal structure; Crystallography, X-Ray; Drug resistance; Drug Resistance, Multiple, Bacterial; Electrophysiology; Escherichia coli - metabolism; Experiments; Gene Transfer, Horizontal; Genes; Guanine - metabolism; Helices; Humanities and Social Sciences; Hydrophobic and Hydrophilic Interactions; Hydrophobicity; Membrane Transport Proteins - chemistry; Membrane Transport Proteins - metabolism; Membranes; Metabolites; Models, Molecular; multidisciplinary; Multidrug resistance; Multidrug resistant organisms; Proteins; Riboswitch; Science; Science (multidisciplinary); Selectivity; Substrate Specificity; Substrates; Topology
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-19820-8

By providing broad resistance to environmental biocides, transporters from the small multidrug resistance (SMR) family drive the spread of multidrug resistance cassettes among bacterial populations. A fundamental understanding of substrate selectivity by SMR transporters is needed to identify the types of selective pressures that contribute to this process. Using solid-supported membrane electrophysiology, we find that promiscuous transport of hydrophobic substituted cations is a general feature of SMR transporters. To understand the molecular basis for promiscuity, we solved X-ray crystal structures of a SMR transporter Gdx-Clo in complex with substrates to a maximum resolution of 2.3 Å. These structures confirm the family’s extremely rare dual topology architecture and reveal a cleft between two helices that provides accommodation in the membrane for the hydrophobic substituents of transported drug-like cations. Gdx-Clo is a bacterial transporter from the small multidrug resistance (SMR) family. Here, the authors use solid supported membrane electrophysiology to characterize Gdx-Clo functionally and report crystal structures of Gdx-Clo which confirm the dual topology architecture and offer insight into substrate binding and transport mechanism.