An elastic protein from the cortical layer of the sea-urchin egg.

An elastic protein was isolated from the cortical layer of the fertilized eggs of two species of sea-urchin. Young's modulus of the fiber of the sea-urchin protein was approximately 1-10(7) dyne/cm2. The amino acid compositions of the elastic protein from the two species of sea-urchin eggs were very similar to that of connectin, elastic protein from vertebrate skeletal muscle. The fluorescent antibody against muscle connectin stained the cortical layer of the sea-urchin egg. It appears that the elastic protein is responsible for the elasticity of the egg cortex.