Characterization of (Ca2+ + Mg2+) adenosine triphosphatase activity and calcium transport in boar sperm plasma membrane vesicles and their relation to phosphorylation of plasma membrane proteins.
Properties of (Ca2+ + Mg2+) adenosine triphosphatase (ATPase) in plasma membranes from boar epididymal spermatozoa are described. Enzyme activity is optimum at high pH and has a high affinity for Ca2+. It is not inhibited by the calmodulin antagonist trifluoperazine (TFP), but it is inhibited by low concentrations of Ca2+. Plasma membrane vesicles obtained by hypotonic lysis of intact sperm [mixed inside-out (IOV) and right side-out (ROV) vesicles] transport 45Ca2+ in the presence of oxalate. Similar to the Ca2+-stimulated Mg ATPase activity, transport is unaffected by TFP, but unlike the ATPase, transport is at an optimum rate near neutral pH and is completely inhibited by p-chloromercurphenylsulfonate (pCMS). When plasma membranes are labeled in the presence and absence of Ca2+ and Mg2+ with [gamma-32P]ATP, differences in the intensity of labeling and lability of bound 32P to alkali and hydroxylamine suggest that two polypeptides between 100-120K may be related to a transport ATPase. The addition of TFP at concentrations which stimulate net Ca2+ uptake in intact cells causes intense labeling of a single neutrally charged protein near 68K. These labeling patterns and the properties of (Ca2+ + Mg2+) ATPase identify particular plasma membrane proteins (PMPs) from the complex surface of these cells that may be involved in Ca2+-dependent functions and support the view that calmodulin is not directly involved in the regulation of ATP-driven Ca2+ efflux from boar spermatozoa.
D000818:Animals; D001693:Biological Transport, Active; D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008970:Molecular Weight; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D013094:Spermatozoa / Q000201:enzymology*; D013552:Swine
D008565:Membrane Proteins; D010750:Phosphoproteins; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium