Characterization of Ca(2+)-ATPase in rod outer segment disk membranes.
The Ca(2+)-pump isolated in rod outer segment disk membranes as aspartylphosphate intermediate E-P has been characterized: the 100 kDa phosphoprotein was completely inhibited by thapsigargin, was not sensitive to digestion by calpain, and displayed a tryptic digestion pattern with the formation of two autophosphorylatable fragments of about 55 and 35 kDa. These results are typical of the calcium pumps of sarcoplasmic or endoplasmic reticulum calcium and differ from those of plasma membrane, such as the Ca(2+)-ATPase of the red blood cells, here shown as controls. The physiological role of calcium pump in disk membranes of vertebrate photoreceptors is discussed in terms of intracellular calcium buffering.
Istituto Policattedra di Chimica Biologica, Università di Genova, Italy.
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I
Panfoli
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Morelli
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Pepe
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006868:Hydrolysis; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014357:Trypsin / Q000378:metabolism
D013729:Terpenes; D019284:Thapsigargin; D014357:Trypsin; D000252:Calcium-Transporting ATPases