Interaction of the heavy chain of scallop myosin heads with skeletal F-actin

The Ca super(2+)-regulated molluscan myosin from scallop muscle and its subfragment 1 (+LC) were cross-linked to skeletal and scallop F-actins by using 1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide (EDC) under conditions avoiding protein aggregation. The elevated Mg super(2+)-ATPase of the covalent acto-S-1 was as high in the absence as in the presence of Ca super(2+). In contrast, the cross-linking of the intact myosin to actin led to an enhancement of the Mg super(2+)-ATPase that was 2-fold higher in the presence than in the absence of Ca super(2+). Calcium had no effect on the stimulated ATPase of the covalent complex formed with desensitized myosin.