ISOLATION AND CHARACTERIZATION OF THE HIGH-AFFINITY K+-TRANSLOCATING ATPASE FROM RHODOBACTER-SPHAEROIDES

Cells of the purple nonsulfur bacterium Rhodobacter sphaeroides express a high-affinity K+ uptake system when grown in media with low K+ concentrations. A vanadate-sensitive, K+-stimulated and Mg2+-stimulated ATPase was purified from membranes of these cells by solubilization with decyl-beta-D-maltoside in the presence of Escherichia coli phospholipids followed by triazine-dye affinity chromatography. This primary transport system has a substrate specificity and an inhibitor sensitivity closely similar to those of the Kdp ATPase from E. coli and is composed of three subunits with molecular masses of 70.0, 43.5, and 23.5 kDa.