Calcium adenosinetriphosphatase of bovine retinal rod outer segment disks.
A Ca(2+)-pumping ATPase activity is present in bovine retinal rod outer segment purified disks. The ATPase has a high Ca2+ affinity (KM = 25 microM). Low Ca2+ (n-microM) concentrations stimulate an ATP-dependent Ca2+ uptake and the ATP hydrolysis in the absence of exogenous Mg2+. Electrophoretic analysis of disk proteins after treatment with (gamma-32P)ATP shows the existence of the enzyme-phosphate acid-stable, hydroxylamine-sensitive intermediate complex of molecular mass of about 135 kDa. The results would indicate the presence of an inwardly directed Ca(2+)-ATPase pump acting on the disk membrane, that could be involved in the regulation of cytosolic free Ca2+ levels inside ROS.
Panfoli
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I
Istituto di Chimica Biologica, Università di Genova.
Morelli
A
A
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000032:analysis*; D002417:Cattle; D005246:Feedback; D012374:Rod Cell Outer Segment / Q000201:enzymology*
D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases