Publication Date:
2010-09-25
Description:
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.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2946090/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2946090/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Long, Feng -- Su, Chih-Chia -- Zimmermann, Michael T -- Boyken, Scott E -- Rajashankar, Kanagalaghatta R -- Jernigan, Robert L -- Yu, Edward W -- GM 072014/GM/NIGMS NIH HHS/ -- GM 074027/GM/NIGMS NIH HHS/ -- GM 081680/GM/NIGMS NIH HHS/ -- GM 086431/GM/NIGMS NIH HHS/ -- R01 GM072014/GM/NIGMS NIH HHS/ -- R01 GM074027/GM/NIGMS NIH HHS/ -- R01 GM074027-05/GM/NIGMS NIH HHS/ -- R01 GM086431/GM/NIGMS NIH HHS/ -- R01 GM086431-01A2/GM/NIGMS NIH HHS/ -- RR-15301/RR/NCRR NIH HHS/ -- England -- Nature. 2010 Sep 23;467(7314):484-8. doi: 10.1038/nature09395.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Molecular, Cellular and Developmental Biology Interdepartmental Graduate Program, Iowa State University, Iowa 50011, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20865003" target="_blank"〉PubMed〈/a〉
Keywords:
Apoproteins/chemistry/metabolism
;
Binding Sites
;
Cell Membrane/metabolism
;
Copper/chemistry/*metabolism
;
Crystallography, X-Ray
;
Cytosol/metabolism
;
Escherichia coli/*chemistry
;
Escherichia coli Proteins/*chemistry/*metabolism
;
Ion Transport
;
Membrane Transport Proteins/*chemistry/*metabolism
;
Methionine/*metabolism
;
Models, Biological
;
Models, Molecular
;
Periplasm/metabolism
;
Protein Structure, Quaternary
;
Protein Structure, Tertiary
;
Silver/chemistry/*metabolism
;
Structure-Activity Relationship
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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