Fig. 6. PKC phosphorylation change following the initiation of motility in intact sea urchin spermatozoa. The presence of PKC and its catalytic cleavage product (arrowheads) was evidenced by immunoblotting with an anti-phospho-PKC antibody (pan). The protein phosphorylation profile obtained with the anti-phospho-PKC substrate antibody (subs) is presented for comparison. i, immotile; m, motile. A blot representative of two other blots is presented.