ATP synthesis in the disk membranes of rod outer segments of bovine retina
Pepe, I.M.; Notari, L.; Cugnoli, C.; Panfoli, I.; Morelli, A.
Journal of Photochemistry and Photobiology. B Biology 66(2): 148-152
ATP is synthesized on the disk membrane isolated from rod outer segments of the bovine retina. Together with a slow component which accounted for a constant rate of about 22 nmol ATP/min/mg of protein and which was due to the adenylate kinase activity, a fast component with a maximal activity of about 58 nmol ATP/min/mg of protein was measured at physiological calcium concentrations. This fast activity disappeared in the presence of the Ca(2+) ionophore A23187, was inhibited by vanadate or thapsigargin but not by oligomycin, suggesting that this ATP synthesis is due to the reversal functioning of the Ca(2+)-ATPase previously found on the disk membranes.