Studies on sulfhydryl groups during cell division of sea urchin egg. III. SH groups of KC1-soluble proteins and their change during cleavage.

Sea urchin egg proteins extracted with KCl are mostly TCA-soluble and, conversely, those extracted with TCA are KCl-soluble. Both groups are water-insoluble and show fluctuations in-SH content during the division cycle. The fluctuation of the-SH groups of the KCl-soluble protein of the whole egg is due to a -SHright harpoon over left harpoon-S-S- interchange within the freely reacting groups and not within the sluggish and masked -SH groups of the protein. The -SH content of the KCl-soluble protein of the egg cortex also fluctuates in a similar way.