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).
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Institut National de la Santé et de la Recherche Médicale, Faculté de Pharmacie, Montpellier, France.
Bouvagnet
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Walzthöny
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Léger
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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