Chloride ATPase in Marine Algae

Abstract

It is generally accepted that the outer membrane of eukaryotic cells operates a P-type ATPase, i.e., an ATPase which is temporarily phosphorylated during the enzymatic reaction cycle (Pedersen and Carafoli 1987). The characteristic inhibition of these ATPases by vanadate is consequently understood as competition for the phosphate binding site. The intact catalytic entity in the native membrane is a homodimer with phosphohydrolytic subunits of about 100 kDa. There are P-type ATPases of different specificity with respect to the transported substrate(s). In animal cells, P-type ATPases are known for uniport, e.g., of Ca²⁺ (review: Carafoli 1991) or H⁺ (Kinne-Saffran 1989) and for antiport, e.g., of H⁺/K⁺ (Forte et al. 1989) or of Na⁺/K⁺ (Skou 1965), the latter being probably the most familiar P-type ATPase.