title: Interaction of myotoxin a with the Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum.
abstract: Myotoxin a is a muscle-damaging toxin isolated from the venom of Crotalus viridis viridis. Its interaction with the Ca2+-ATPase of sarcoplasmic reticulum (SR) vesicles purified from rabbit skeletal muscle was investigated. Myotoxin a inhibited Ca2+ loading and stimulated Ca2+-dependent ATPase without affecting unidirectional Ca2+ efflux. Its action was dose, time, and temperature dependent. Myotoxin a partially blocked the binding of specific anti-(rabbit SR Ca2+-ATPase) antibodies. It is concluded that myotoxin a attaches to the SR Ca2+-ATPase and uncouples Ca2+ uptake from Ca2+-dependent ATP hydrolysis. Myotoxin a also prevented the formation of decavanadate-induced two-dimensional crystalline arrays of the SR Ca2+-ATPase.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D003435:Crotalid Venoms / Q000378:metabolism / Q000494:pharmacology*; D003460:Crystallization; D004797:Enzyme-Linked Immunosorbent Assay; D008854:Microscopy, Electron; D011108:Polymers; D011485:Protein Binding; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology*; D013696:Temperature; D014638:Vanadates; D014639:Vanadium
chemical_list: D003435:Crotalid Venoms; D011108:Polymers; D014639:Vanadium; D014638:Vanadates; C018932:myotoxin A; D000252:Calcium-Transporting ATPases; D002118:Calcium