Campus Units

Biochemistry, Biophysics and Molecular Biology, Roy J. Carver Department of, Chemistry, Physics and Astronomy, Bioinformatics and Computational Biology, Molecular, Cellular and Developmental Biology

Document Type

Article

Publication Version

Accepted Manuscript

Publication Date

2010

Journal or Book Title

Nature

Volume

467

Issue

7314

First Page

484

Last Page

488

DOI

10.1038/nature09395

Abstract

Gram-negative bacteria, such as Escherichia coli, frequently utilize tripartite efflux complexes in the resistance-nodulation-cell division (RND) family to expel diverse toxic compounds from the cell.1,2 The efflux system CusCBA is responsible for extruding biocidal Cu(I) and Ag(I) ions.3,4 No prior structural information was available for the heavy-metal efflux (HME) subfamily of the RND efflux pumps. Here we describe the crystal structures of the inner membrane transporter CusA in the absence and presence of bound Cu(I) or Ag(I). These CusA structures provide important new structural information about the HME sub-family of RND efflux pumps. The structures suggest that the metal binding sites, formed by a three-methionine cluster, are located within the cleft region of the periplasmic domain. Intriguingly, this cleft is closed in the apo-CusA form but open in the CusA-Cu(I) and CusA-Ag(I) structures, which directly suggests a plausible pathway for ion export. Binding of Cu(I) and Ag(I) triggers significant conformational changes in both the periplasmic and transmembrane domains. The crystal structure indicates that CusA has, in addition to the three-methionine metal binding site, four methionine pairs - three located in the transmembrane region and one in the periplasmic domain. Genetic analysis and transport assays suggest that CusA is capable of actively picking up metal ions from the cytosol, utilizing these methionine pairs/clusters to bind and export metal ions. These structures suggest a stepwise shuttle mechanism for transport between these sites.

Comments

This is a manuscript of an article published as Long, Feng, Chih-Chia Su, Michael T. Zimmermann, Scott E. Boyken, Kanagalaghatta R. Rajashankar, Robert L. Jernigan, and Edward W. Yu. "Crystal structures of the CusA efflux pump suggest methionine-mediated metal transport." Nature 467, no. 7314 (2010): 484. doi: 10.1038/nature09395. Posted with permission.

Copyright Owner

Macmillan Publishers Limited

Language

en

File Format

application/pdf

Published Version

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