Mechanism of Cu+-transporting ATPases: soluble Cu+ chaperones directly transfer Cu+ to transmembrane transport sites.
As in other P-type ATPases, metal binding to transmembrane metal-binding sites (TM-MBS) in Cu(+)-ATPases is required for enzyme phosphorylation and subsequent transport. However, Cu(+) does not access Cu(+)-ATPases in a free (hydrated) form but is bound to a chaperone protein. Cu(+) transfer from Cu(+) chaperones to regulatory cytoplasmic metal-binding domains (MBDs) present in these ATPases has been described, but there is no evidence of a proposed subsequent Cu(+) movement from the MBDs to the TM-MBS. Alternatively, we postulate the parsimonious Cu(+) transfer by the chaperone directly to TM-MBS. Testing both models, the delivery of Cu(+) by Archaeoglobus fulgidus Cu(+) chaperone CopZ to the corresponding Cu(+)-ATPase, CopA, was studied. As expected, CopZ interacted with and delivered the metal to CopA MBDs. Cu(+)-loaded MBDs, acting as metal donors, were unable to activate CopA or a truncated CopA lacking MBDs. Conversely, Cu(+)-loaded CopZ activated the CopA ATPase and CopA constructs in which MBDs were rendered unable to bind Cu(+). Furthermore, under nonturnover conditions, CopZ transferred Cu(+) to the TM-MBS of a CopA lacking MBDs. These data are consistent with a model where MBDs serve a regulatory function without participating in metal transport and the chaperone delivers Cu(+) directly to transmembrane transport sites of Cu(+)-ATPases.
González-Guerrero
Manuel
M
Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA.
Argüello
José M
JM
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019611:Archaeoglobus fulgidus / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003300:Copper / Q000378:metabolism*; D000073840:Copper-Transporting ATPases; D004789:Enzyme Activation; D017136:Ion Transport; D008954:Models, Biological; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics
D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D002413:Cations, Divalent; D018832:Molecular Chaperones; D003300:Copper; D000251:Adenosine Triphosphatases; D000073840:Copper-Transporting ATPases