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Title: Uncovering the transmembrane metal binding site of the novel bacterial major facilitator superfamily-type copper importer CcoA

In this study, uptake and trafficking of metals and their delivery to their respective metalloproteins are important processes. Cells need precise control of each step to avoid exposure to excessive metal concentrations and their harmful consequences. Copper (Cu) is a required micronutrient used as a cofactor in proteins. However, in large amounts, it can induce oxidative damage; hence, Cu homeostasis is indispensable for cell survival. Biogenesis of respiratory heme-Cu oxygen (HCO) reductases includes insertion of Cu into their catalytic subunits to form heme-Cu binuclear centers. Previously, we had shown that CcoA is a major facilitator superfamily (MFS)-type bacterial Cu importer required for biogenesis of cbb 3-type cytochrome coxidase ( cbb 3-Cox). Here, using Rhodobacter capsulatus, we focused on the import and delivery of Cu to cbb 3-Cox. By comparing the CcoA amino acid sequence with its homologues from other bacterial species, we located several well-conserved Met, His, and Tyr residues that might be important for Cu transport. We determined the topology of the transmembrane helices that carry these residues to establish that they are membrane embedded, and substituted for them amino acids that do not ligand metal atoms. Characterization of these mutants for their uptake of radioactive 64Cu and cbbmore » 3-Cox activities demonstrated that Met233 and His261 of CcoA are essential and Met237 and Met265 are important, whereas Tyr230 has no role for Cu uptake or cbb3-Cox biogenesis. These findings show for the first time that CcoA-mediated Cu import relies on conserved Met and His residues that could act as metal ligands at the membrane-embedded Cu binding domain of this transporter.« less
 [1] ;  [1] ;  [2] ;  [1]
  1. Univ. of Pennsylvania, Philadelphia, PA (United States)
  2. Albert-Ludwigs Univ. of Freiburg, Freiburg (Germany)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
mBio (Online)
Additional Journal Information:
Journal Name: mBio (Online); Journal Volume: 7; Journal Issue: 1; Related Information:; Journal ID: ISSN 2150-7511
American Society for Microbiology
Research Org:
Univ. of Pennsylvania, Philadelphia, PA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
OSTI Identifier: