The Copper-transporting ATPases, Menkes and Wilson Disease Proteins, Have Distinct Roles in Adult and Developing Cerebellum

Functional and Biochemical Characterization of Cucumber Genes Encoding Two Copper ATPases CsHMA5.1 and CsHMA5.2

“…However, different expression of CsHMA5.1 and CsHMA5.2 in cucumber organs suggests different biological roles for the two cucumber HMA5s. When studied in yeast vacuolar membranes, CsHMA5.1 and CsHMA5.2 were activated in the presence of copper and silver, similarly to homologous proteins in bacteria (CopA), humans (ATP7A and ATP7B), and A. thaliana (PAA1) (12,(35)(36)(37)(38), confirming that they are putative copper ATPases. Interestingly, the maximal copper-dependent ATPase activity of CsHMA5.1 and CsHMA5.2 required the presence of Cys and reducing agents (DTT and Na 2 SO 3 ) in the assay medium.…”

“…ATPase and Transport Activity of CsHMA5.1 and CsHMA5.2-Copper ATPases characterized so far, CopA, ATP7A, ATP7B, and PAA1/HMA6, required monovalent copper for maximal activation of their ATPase activity (12,(35)(36)(37)(38). To establish whether copper or other metals are essential for CsHMA5.1-mediated and CsHMA5.2-mediated ATP hydrolysis, we studied the ATPase activity in vacuolar membranes isolated from the ⌬ycf1 strain expressing CsHMA5.1-GFP or CsHMA5-GFP.…”

Biochemical basis of regulation of human copper-transporting ATPases

“…Similarly, the in vitro experiments indicate that the functional characteristics of human Cu-ATPases, ATP7A and ATP7B, are distinct, perhaps contributing to their specific physiological roles. When compared under identical conditions in vitro, the membrane-bound ATP7A shows faster phosphorylation from ATP and it also dephosphorylates more rapidly (25). This observation suggests that the ATP7A turnover and copper transport rates are probably higher.…”

“…Therefore characterizing factors that affect the dephosphorylation step may provide some insight into the regulation of copper release. It is interesting, that under identical conditions in vitro ATP7A shows 6-fold faster dephosphorylation compared to ATP7B (25). Given high sequence similarity of their trans-membrane portions it seems plausible that the difference in the rate of dephosphorylation of these two Cu-ATPases (and/or copper release) could be associated with the structural variations in their luminal loop(s).…”

“…By analogy with other P-type ATPases, the binding of copper from the cytosolic side is thought to take place when the protein is present in the so-called E1-state, which is characterized by high affinity of the intramembrane sites for the transported ion. The measurements of copper-dependence of catalytic phosphorylation yielded apparent affinity of these sites for copper in the range of 0.7-2.5 μM (25,26). Copper binding to the intra-membrane sites is associated with the transfer of γ-phosphate of ATP to the Cu-ATPase and transient stabilization of the phosphorylated state of the protein E1P ( Figure 2B).…”