Purification and properties of caldesmon-like protein from molluscan smooth muscle

In this comparative study, the heat-stable protein content of scallop muscles was reinvestigated. The hCaD-like protein was prepared and its properties carefully examined. The heat-stable high-molecular-mass caldesmon-like (hCaD-like) protein is only present in the catch (smooth) muscle and it is completely absent in the striated muscle of scallop. The isolated scallop hCaD-like protein cosediments with F-actin, binds to myosin significantly and inhibits the ATPase activity of acto-myosin. A partial cDNA clone from a Mytilus anterior byssus retractor muscle (ABRM)-related protein showed strong homology with the hCaD gizzard sequence. This allowed identification of the heat-stable 100-110 kDa protein doublet band isolated in this study as a caldesmon-like molecule.