Regulation of sperm flagellar movement by protein phosphorylation and dephosphorylation.

Flagellar motility of Triton models of sea urchin spermatozoa was reactivated by cyclic AMP-dependent protein kinase and a protein factor, termed motility activator, both of which were prepared from the detergent-extract of sea urchin spermatozoa. It was shown that phosphorylation of the motility activator by the protein kinase is necessary for the reactivation of flagellar motility [Ishiguro et al, J. Cell Biol. 92:777-782, 1982; Murofushi et al, in "Biological Functions of Microtubules and Related Structures," Academic Press, 1982]. Reactivating factor was also detected in a KCl-extract of the axoneme fraction devoid of the detergent-extractable materials. The activity of this factor was also cyclic AMP- and protein kinase-dependent. Furthermore, when freshly prepared Triton models were treated with phosphoprotein phosphatase prepared from bovine cardiac muscle, the flagellar motility was drastically suppressed. This inhibition of the motility was partially recovered by the addition of cyclic AMP and protein kinase to the phosphatase-treated models.