title: Site-specific photo-cross-linking studies on interactions between troponin and tropomyosin and between subunits of troponin.
abstract: We have used the sulfhydryl-specific heterobifunctional photo-cross-linker 4-maleimidobenzophenone (BP-Mal) to study the interactions of rabbit skeletal tropomyosin with troponin and of the troponin subunits with each other. We found that alpha,alpha-tropomyosin specifically labeled at Cys-190 with BP-Mal photo-cross-links with all three subunits of troponin with decreasing cross-linking yields in the order of troponin T, troponin I, and troponin C. There was no apparent Ca2+ dependence in the cross-linking yields. In separate experiments, we found that troponin C labeled specifically at Cys-98 with BP-Mal photo-cross-links to both troponin I and troponin T in the two binary complexes, as well as in the ternary complex. Again, no Ca2+-dependent changes in the cross-linking yields were detectable. These results are in general agreement with the picture that troponin I and troponin T are in close contact with troponin C near its Cys-98 and that all three troponin subunits are in the proximity of Cys-190 of tropomyosin.
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001577:Benzophenones / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D046911:Macromolecular Substances; D008301:Maleimides; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism*; D011817:Rabbits; D014316:Tritium; D014335:Tropomyosin / Q000378:metabolism*; D014336:Troponin / Q000378:metabolism*
chemical_list: D000199:Actins; D001577:Benzophenones; D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D008301:Maleimides; D014335:Tropomyosin; D014336:Troponin; D014316:Tritium; D004533:Egtazic Acid; C046109:benzophenone-4-maleimide; D002118:Calcium