CHARACTERIZATION OF THE PLASMALEMMA ATPASE FROM THE CYANOBACTERIA SYNECHOCOCCUS PCC-6311 AND PCC-7942

Biochemical properties of the ATPase from the plasma membrane of the cyanobacteria Synechococcus PCC 6311 and PCC 7942 were examined. ATPase activity associated with purified plasma membrane vesicles was strongly inhibited by 100 μM vanadate (87%), 100 μM diethyistilbestrol (70%) and 100 mM fluoride ions (83%). No inhibition was observed in the presence of dicyclohexylcarbodiimide, nitrate, azide, or molybdate. A 50% activation was observed in the presence of 50 mM KCl but none was observed in the presence of NaCl or NH4Cl. This ATPase was able to form a pH gradient, the amplitude of which was decreased by the presence of 100 μM vanadate. On Western blot of the plasmalemma proteins, no labeling was observed with a monoclonal antibody against the β subunit of the F0-F1 ATPase, although staining was observed with the 55-kDa subunit of the thylakoid membrane ATPase. After phosphorylation of plasmalemma vesicles, by [γ-32P]ATP, the autoradiograms of the electrophoreses, performed under acid conditions, exhibited labeling of a 110-kDa protein. The results indicated that the Synechococcus plasma membrane ATPase can be classified as a H+ translocating P-type ATPase and compared to the plant plasmalemma ATPase. © 1993 Academic Press. All rights reserved.