title: The cross-linking of rabbit skeletal muscle sarcoplasmic reticulum protein.
abstract: Sarcoplasmic reticulum proteins have been cross-linked in situ with two reagents, the disulphide-bridged bifunctional imido ester, dimethyl-3,3'-dithiobispropionimidate dihydrochloride and the mild oxidant cupric phenanthroline. Analysis of proteins so cross-linked by electrophoresis on agarose/acrylamide gels reveals that a series of new polypeptides, up to a molecular weight of 900 000, are formed. These have molecular weights which are multiples of 100 000. Further analysis of samples by electrophoresis in a second dimensions containing a reducing agent revealed the monomeric polypeptides from which the cross-linked polypeptides were formed. With dimethyl 3,3'-dithiobispropionimidate dihydrochloride homopolymers of the Ca2+-stimulated ATPase, calsequestrin and/or calcium binding protein were formed. With cupric phenanthroline only the Ca2+-stimulated ATPase was involved in polymer formation. It has been confirmed on another gel system that these two proteins which are involved in Ca2+ binding are not cross-linked intermolecularly with this latter reagent. We conclude that the 100 000 dalton Ca2+-stimulated ATPase polypeptides are within 2 A of each other in the membrane while calsequestrin and/or calcium binding protein are within 11 A of each other. Although there appears to be no limit to the extent of cross-linking of any of these polypeptides there is not indication of heteropolymer associations between them.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002155:Calsequestrin / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D046911:Macromolecular Substances; D008970:Molecular Weight; D009124:Muscle Proteins / Q000302:isolation & purification / Q000378:metabolism; D009132:Muscles; D011485:Protein Binding; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure*
chemical_list: D002155:Calsequestrin; D002352:Carrier Proteins; D046911:Macromolecular Substances; D009124:Muscle Proteins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D002118:Calcium