Factor XIIIa-catalyzed cross-linking of platelet and muscle actin. Regulation by nucleotides.

Actin from human blood platelets or rabbit skeletal muscle can serve as substrate for factor XIIIa. The latter catalyzes the incorporation of 1.5-2 mol monodansylcadaverine/mol rabbit actin and 0.5 mol/mol platelet actin. Highly cross-linked platelet and muscle actin polymers form in the absence of added amines, indicating the presence of both acceptor and donor sites. As expected, the cross-link was found to be a gamma-glutamyl-epsilon-lysine bone, with an average of 0.3-0.4 mol dipeptide/mol platelet actin. Both cross-linking and amine incorporation are prevented by ATP, ADP, GTP, CTP, but not by AMP and cyclic AMP. These nucleotides may have important regulatory role in muscle and non-muscle systems.