MONOCLONAL-ANTIBODIES AGAINST THE PROTEIN COMPLEX THAT CONTAINS THE FLAGELLAR MOVEMENT-INITIATING PHOSPHOPROTEIN OF ONCORHYNCHUS-KETA

We isolated and characterized several monoclonal antibodies against a protein complex containing the flagellar movement-initiating phosphopr otein (MIPP) that appears to play a crucial role in the initiation of flagellar movement in quiescent spermatozoa of Salmonid fish. The effe cts of the antibodies on the phosphorylation of MIPP, as well as on th e initiation of movement, in model sperm cells were studied. Three mon oclonal antibodies, namely, FMI7, FMI18, and FMI27, were found specifi cally to inhibit both the initiation of flagellar movement and the pho sphorylation of MIPP. These antibodies did not recognize denatured MIP P; they only recognized the native antigen. FMI7 exclusively recognize d the denatured form of a 38-kDa protein, which may possibly be a prot ein kinase responsible for the phosphorylation of MIPP. Immunofluoresc ence analysis in situ of model sperm cells with the antibodies showed that the antigen was localized predominantly in the basal structure of the spermatozoon. Thus, the results clearly demonstrate the involveme nt of MIPP in the initiation of flagellar movement and the control of flagellar motility.