CORTEX PROTEIN OF SEA URCHIN EGGS I. ITS PURIFICATION AND OTHER PROTEIN COMPONENTS OF THE CORTEX

Isolated cortical hull of the sea urchin egg consisted of a gel layer having 3-4 μ in thickness which could be dispersed with 0.6 m KCl. After removing a protein fraction soluble in 10 mm Tris-HCl buffer (pH 7.0-7.2) containing 1 mm ATP or EDTA and 1 mm GSH, so called KCl-soluble protein of the cortices was obtained. After purifying the "cortex protein", it was homogeneous so far as checked by ultracentrifugation and electrophoresis on a polyacrylamide gel. The cortex protein had a thiol-disulfide exchange activity to Ca-insoluble protein in the ATP-extract of the cortices catalyzed by a transhydrogenase. Neither ovoactin nor actomyosin-like protein was detected in the ATP-extract or the 0.6 m KCl-extract of the cortices respectively. Hyalin was not detected in our KCl-soluble protein fractions of isolated cortices.