3KSS

Structure and Mechanism of the Heavy Metal Transporter CusA

Summary for 3KSS

• Entry DOI: 10.2210/pdb3kss/pdb
• Related: 3KSO
• Descriptor: Cation efflux system protein cusA, COPPER (I) ION (2 entities in total)
• Functional Keywords: transmembrane helix, cell inner membrane, cell membrane, copper transport, ion transport, membrane, transmembrane, transport, metal transport
• Biological source: Escherichia coli
• Cellular location: Cell inner membrane ; Multi- pass membrane protein : P38054
• Total number of polymer chains: 1
• Total formula weight: 115897.49

Authors

Su, C.-C. (deposition date: 2009-11-23, release date: 2010-09-22, Last modification date: 2024-02-21)

Primary citation

Long, F.,Su, C.C.,Zimmermann, M.T.,Boyken, S.E.,Rajashankar, K.R.,Jernigan, R.L.,Yu, E.W.
Crystal structures of the CusA efflux pump suggest methionine-mediated metal transport.
Nature, 467:484-488, 2010

PubMed Abstract: Gram-negative bacteria, such as Escherichia coli, frequently use tripartite efflux complexes in the resistance-nodulation-cell division (RND) family to expel various toxic compounds from the cell. The efflux system CusCBA is responsible for extruding biocidal Cu(I) and Ag(I) ions. No previous 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 new structural information about the HME subfamily 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. 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, using these methionine pairs or clusters to bind and export metal ions. These structures suggest a stepwise shuttle mechanism for transport between these sites.

PubMed: 20865003
DOI: 10.1038/nature09395

Experimental method

X-RAY DIFFRACTION (3.88 Å)