Visualization of cardiac ventricular myosin heavy chain homodimers and heterodimers by monoclonal antibody epitope mapping.
Two mAbs, one specific for cardiac alpha-myosin heavy chains (MHC) and the other specific for cardiac beta-MHC, were used to investigate the heavy-chain dimeric organization of rat cardiac ventricular myosin. Epitopes of the two mAbs were mapped on the myosin molecule by electron microscopy of rotary shadowed mAb-myosin complexes. mAbs were clearly identifiable by the different locations of their binding sites on the myosin rod. Thus, myosin molecules could be directly discriminated according to their alpha-or beta-MHC content. alpha alpha-MHC and beta beta-MHC homodimers were visualized in complexes consisting of two molecules of the same mAb bound to one myosin molecule. By simultaneously using the alpha-MHC-specific mAb and the beta-MHC-specific mAb, alpha beta-MHC heterodimers were visualized in complexes formed by one molecule of each of the two mAbs bound to one myosin molecule. Proportions of alpha alpha-and beta beta-MHC homodimers and alpha beta-MHC heterodimers were estimated from quantifications of mAb-myosin complexes and compared with the proportions given by electrophoreses under nondenaturing conditions. This visualization of cardiac myosin molecules clearly demonstrates the arrangement of alpha- and beta-MHC in alpha alpha-MHC homodimers, beta beta-MHC homodimers, and alpha beta-MHC heterodimers, as initially proposed by Hoh, J. F. Y., G. P. S. Yeoh, M. A. W. Thomas, and L. Higginbottom (1979).
Institut National de la Santé et de la Recherche Médicale, Faculté de Pharmacie, Montpellier, France.
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Dechesne
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Bouvagnet
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Walzthöny
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Léger
D000818:Animals; D000911:Antibodies, Monoclonal; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D009206:Myocardium / Q000648:ultrastructure*; D009218:Myosins / Q000502:physiology*; D011485:Protein Binding; D051381:Rats
D000911:Antibodies, Monoclonal; D046911:Macromolecular Substances; D009218:Myosins