A novel P-type Cl(-)-stimulated ATPase: phosphorylation and specificity.

Utilizing a proteoliposomal preparation containing Cl(-)-ATPase, it was demonstrated that [gamma-32P]ATP-induced phosphorylation of this pump is by way of a relatively low binding affinity while protein dephosphorylation was accelerated by increasing concentrations of unlabeled ATP. Ca2+ and Mn2+ were also shown to stimulate phosphorylation of the enzyme, but to a much lesser extent than Mg2+. Orthovanadate inhibition of enzyme phosphorylation was directly related to its concentration. These results suggested that the Cl(-)-pump was a P-type ATPase similar to that found in plants and fungi based upon its low-affinity phosphorylation kinetics.