Calcium-dependent regulation of the motor activity of recombinant full-length Physarum myosin.

We successfully synthesized full-length and the mutant Physarum myosin and heavy meromyosin (HMM) constructs associated with Physarum regulatory light chain and essential light chain (PhELC) using Physarum myosin heavy chain in Sf-9 cells, and examined their Ca2+-mediated regulation. Ca2+ inhibited the motility and ATPase activities of Physarum myosin and HMM. The Ca2+ effect is also reversible at the in vitro motility of Physarum myosin. We demonstrated that full-length myosin increases the Ca2+ inhibition more effectively than HMM. Furthermore, Ca2+ did not affect the motility and ATPase activities of the mutant Physarum myosin with PhELC that lost Ca2+-binding ability. Therefore, we conclude that PhELC plays a critical role in Ca2+-dependent regulation of Physarum myosin.