A Myosin-like Protein in the Cortical Layer of the Sea Urchin Egg

An interaction between actinand myosin-like proteins and its implication in cellular motilities have been suggested in a variety of cells other than muscle (reviewed by Taylor, 1972, and by Rebhun, 1972) . Actually, those proteins have been extracted and purified from certain kinds of cells . They may be located mainly in the cell cortex (Ishikawa et al ., 1969) . In sea urchin eggs, although an actin-like protein which could interact with rabbit skeletal muscle myosin in a manner similar to muscle actin was extracted and purified from acetone powder of whole cell (Miki-Noumura and Oosawa, 1969), an actomyosin-like component has not been detected in the isolated cortex (Mabuchi and Sakai, 1972) . However, extensive studies on this line have confirmed that a myosin-like component was contained in the 0 .6 M KCl-extract of the isolated cortex of the sea urchin egg . It will be called "ovomyosin" in this paper .