A MONOCLONAL-ANTIBODY AGAINST THE DYNEIN IC1 PEPTIDE OF SEA-URCHIN SPERMATOZOA INHIBITS THE MOTILITY OF SEA-URCHIN, DINOFLAGELLATE, AND HUMAN FLAGELLAR AXONEMES

To investigate the role of axonemal components in the mechanics and re gulation of flagellar movement, we have generated a series of monoclon al antibodies (mAb) against sea urchin (Lytechinus pictus) sperm axone mal proteins, selected for their ability to inhibit the motility of de membranated sperm models. One of these antibodies, mAb D1, recognizes an antigen of 142 kDa on blots of sea urchin axonemal proteins and of purified outer arm dynein, suggesting that it acts by binding to the h eaviest intermediate chain (IC1) of the dynein arm. mAb D1 blocks the motility of demembranated sea urchin spermatozoa by modifying the beat ing amplitude and shear angle without affecting the ATPase activity of purified dynein or of demembranated immotile spermatozoa. Furthermore , mAb D1 had only a marginal effect on the velocity of sliding microtu bules in trypsin-treated axonemes. This antibody was also capable of i nhibiting the motility of flagella of Oxyrrhis marina, a primitive din oflagellate, and those of demembranated human spermatozoa. Localizatio n of the antigen recognized by mAb D1 by immunofluorescence reveals it s presence on the axonemes of flagella from sea urchin spermatozoa and O. marina but not on the cortical microtubule network of the dinoflag ellate. These results are consistent with a dynamic role for the dynei n intermediate chain IC1 in the bending and/or wave propagation of fla gellar axonemes.