Calcium pump in the disk membranes isolated from bovine retinal rod outer segments.
The existence of a Ca2+ pump in rod outer segment disks of bovine retina is strongly suggested by the isolation on sodium dodecyl sulfate polyacrylamide gel electrophoresis of a hydroxylamine-sensitive phosphorylated intermediate (E-P) of molecular mass of about 100 kDa as well as by measurements of active calcium transport and adenosine 5'-triphosphate (ATP) hydrolysis. Active Ca2+ uptake by disks was dependent on the presence of Mg(2+)-ATP, was inhibited by vanadate or lanthanum and appeared poorly sensitive to calmodulin. ATP hydrolysis by disk membranes was a function of free Ca2+ concentration in the absence of exogenous Mg2+. The presence of a Ca2+ pump on disk membranes is discussed in terms of its possible role in Ca2+ ion buffering during photoreceptor cell functioning.
Istituto Policattedra di Chimica Biologica, Università, Genoa, Italy.
I
I
Panfoli
A
A
Morelli
I M
IM
Pepe
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000302:isolation & purification / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D019811:Hydroxylamine; D006898:Hydroxylamines / Q000494:pharmacology; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D008970:Molecular Weight; D010766:Phosphorylation; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D014638:Vanadates / Q000494:pharmacology
D002147:Calmodulin; D006898:Hydroxylamines; D019811:Hydroxylamine; D014638:Vanadates; D007811:Lanthanum; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium