Fig. 7. Immunolocalization of PKC and phospho-PKC substrates on sea urchin spermatozoa. The presence of PKC and its phosphorylated substrates were evidenced by immunofluorescence with an anti-phospho-PKC antibody (p-PKC pan) and an anti-phospho-PKC substrate (p-PKC subst.) antibody in both immotile and motile spermatozoa (central columns). Labeling of flagellar ß-tubulin with a specific monoclonal antibody (see Materials and methods) is also shown for comparison purposes. In controls without any primary antibody (2^nd Ab only), a weak spot of fluorescence was present at the base of sperm heads. The outer columns show similar images to those in the middle columns but viewed by phase-contrast. Scale bars, 10 µm.