THE ROLE OF THE PROLINE-RICH REGION IN A1-TYPE MYOSIN ESSENTIAL LIGHT-CHAINS - IMPLICATIONS FOR INFORMATION-TRANSMISSION IN THE ACTOMYOSIN COMPLEX

The proline-rich region of A1-type myosin essential light chains funct ions as a spacer arm separating an actin binding site at the extreme N -terminus from the remainder of the protein, Alteration of the length of this region leaving the actin binding site intact results in altere d actin-activated MgATPase kinetics when these light chains are hybrid ised into myosin subfragment-1. In the case of a mutant in which the l ength of the proline-rich region was doubled, actin binding by the lig ht chain was uncoupled from kinetic modulation. The implications of th is result for information transmission in the actomyosin complex are d iscussed.