JBC, Vol. 250, Issue 6, 2085-2094, Mar, 1975

A solid-liquid biphasic model for characterization of properties of muscle and platelet contractile proteins

S. Puszkin, S. Kochwa, E. G. Puszkin and R. E. Rosenfield

Actomyosin, myosin, and actin from different sources are adsorbed, apparently as a monolayer, by polystyrene particles teins for 1 mg of Lytron were about 10-7 liters mol-1, while heterogeneity indices (alpha) varied from 0.70 to 1.0 presumably as a function of spontaneous aggregation in the liquid phase. Adsorption was irreversible. Orientation of absorbed molecules permitted association of bound muscle actin with platelet or muscle myosin. The association constant of the former reaction was 2.78 times 10-6 liters mol-1. Enzymatic properties of adsorbed actomyosin, Mg2+ATPase activity was abolished, but association of myosin with bound actin, or association of actin with bound myosin was accompanied by restoration of Mg2+ATPase activity. Every subunit of F-actin strands, unless F-actin had been fully depolymerized to G-actin, could bind myosin and activate Mg2+ATPase activity. Immunogenic characteristics of muscle myosin were enhanced by Lytron adsorption. Elicited antibodies showed selective specificity for an antigenic determinant located near or at the actin combining site of muscle myosin. Antibodies did not react with actomyosin. Antibodies prevented association of actin with muscle myosin because they inhibited both superprecipitation and development of Mg2+ATPase activity.
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