Key result
Binding of antibodies to the N-terminal segment of actin inhibited both the binding of S-1 to actin in the presence of ATP and a catalytic step in ATP hydrolysis by actomyosin.
Antibodies targeting the N-terminal segment of actin inhibit both myosin S-1 binding and ATP hydrolysis, providing mechanistic insights into the regulation of actomyosin interactions.
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Antibody effects on actin may inform actomyosin models in cardiac research; leaves open translation to human therapeutics.
The binding of myosin subfragment 1 (S-1) to actin in the presence of ATP and the acto-S-1 ATPase activities of acto-S-1 complexes were determined at 5 degrees C under conditions of partial saturation of actin, up to 90%, by antibodies against the first seven N-terminal residues on actin. The antibodies [Fab(1-7)] inhibited strongly the acto-S-1 ATPase and the binding of S-1 to actin in the presence of ATP at low concentrations of S-1, up to 25 microM. Further increases in S-1 concentration resulted in a partial and cooperative recovery of both the binding of S-1 to actin and the acto-S-1 ATPase while causing only limited displacement of Fab(1-7) from actin. The extent to which the binding and the ATPase activity were recovered depended on the saturation of actin by Fab(1-7). The combined amounts of S-1 and Fab binding to actin suggested that the activation of the myosin ATPase activity was due to actin free of Fab. Examination of the acto-S-1 ATPase activities as a function of S-1 bound to actin at different levels of actin saturation by Fab(1-7) revealed that the antibodies inhibited the activation of the bound myosin. Thus, the binding of antibodies to the N-terminal segment of actin can act to inhibit both the binding of S-1 to actin in the presence of ATP and a catalytic step in ATP hydrolysis by actomyosin. The implications of these results to the regulation of actomyosin interaction are discussed.
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Dasgupta et al. (1992) studied this question. Antibodies against the first seven N-terminal residues on actin [Fab(1-7)] was evaluated on Binding of myosin subfragment 1 (S-1) to actin and acto-S-1 ATPase activities. Binding of antibodies to the N-terminal segment of actin inhibited both the binding of S-1 to actin in the presence of ATP and a catalytic step in ATP hydrolysis by actomyosin.
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