Cu+-specific CopB transporter: Revising p1B-type ATPase classification

Rahul Purohit, Matthew O. Ross, Sharon Batelu, April Kusowski, Timothy L. Stemmler, Brian M. Hoffman, Amy C. Rosenzweig*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


The copper-transporting P1B- ATPases, which play a key role in cellular copper homeostasis, have been divided traditionally into two subfamilies, the P1B-1- ATPases or CopAs and the P1B-3- ATPases or CopBs. CopAs selectively export Cu+ whereas previous studies and bioinformatic analyses have suggested that CopBs are specific for Cu2+ export. Biochemical and spectroscopic characterization of Sphaerobacter thermophilus CopB (StCopB) show that, while it does bind Cu2+, the binding site is not the prototypical P1B- ATPase transmembrane site and does not involve sulfur coordination as proposed previously. Most important, StCopB exhibits metal-stimulated ATPase activity in response to Cu+, but not Cu2+, indicating that it is actually a Cu+ transporter. X-ray absorption spectroscopic studies indicate that Cu+ is coordinated by four sulfur ligands, likely derived from conserved cysteine and methionine residues. The histidine-rich N-terminal region of StCopB is required for maximal activity, but is inhibitory in the presence of divalent metal ions. Finally, reconsideration of the P1B- ATPase classification scheme suggests that the P1B-1- and P1B-3-ATPase subfamilies both comprise Cu+ transporters. These results are completely consistent with the known presence of only Cu+ within the reducing environment of the cytoplasm, which should eliminate the need for a Cu2+ P1B- ATPase.

Original languageEnglish (US)
Pages (from-to)2108-2113
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number9
StatePublished - Feb 27 2018


  • CopA
  • CopB
  • Copper efflux
  • Copper homeostasis
  • P1B- ATPase

ASJC Scopus subject areas

  • General


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