Fig. 3. Time course of the phospho-PKC substrate levels following motility initiation of intact sea urchin spermatozoa. The phosphorylation level of the proteins detected with an anti-phospho-PKC substrate antibody increased rapidly (30 s) after transfer of immotile (i) L. pictus spermatozoa into ASW to initiate their motility (m). Protein phosphorylations further increased to a maximum at around 6 min and stayed almost at this level for up to an hour before making a significant drop after 5 h. The arrowheads indicate the position of the 200, 100, 65 and 28 kDa bands. A blot representative of two other blots is presented.