Phosphoenzyme formation by purified, reconstituted copper ATPase of Enterococcus hirae

The Enterococcus hirae CopB ATPase serves in the secretion of excess copper from cells and belongs to the recently discovered, new class of heavy metal transport ATPases. We here report the affinity purification of CopB to near homogeneity and its reconstitution into phospholipid vesicles. In these proteoliposomes, the ATPase formed an acylphosphate reaction intermediate with the gamma-phosphate of ATP. ATPase activity and phosphoenzyme formation were inhibited by vanadate with an I(50) of 0.1 mM. Our results suggest that heavy metal and non-heavy metal ATPases operate by the same underlying mechanism.