Effects of acylpeptide K-26 on the motility of sea urchin sperm model. II. Mechanism of the inhibitory effect of K-26.

Abstract

An acylpeptide called K-26 inhibited the motility of Triton-ex-tracted sea urchin sperm. This inhibition was canceled by the addition of both cAMP and a Triton X-100-soluble fraction of the sperm. The concentration of cAMP that was required to restore the motility was above 1μM. Incorporation of Pi into the Triton-extracted sperm was suppressed by K-26 at the same con-centration as that which inhibited the motility. A factor in the Triton-soluble fraction that was able to cancel the inhibition of the motility by K-26, was par-tially purified by hydroxylapatite and DEAE-cellulose column chromatogra-phies. In both of these steps, the activity to cancel the inhibition of the motility coeluted with that of cAMP-dependent protein kinase (cA kinase). The activity of cA kinase was also inhibited by K-26. The incorporation of Pi into the Triton-extracted sperm was suppressed in the presence of K-26 and was restored by the addition of both cAMP and the cA kinase fraction. From these results, it was suggested that K-26 affects the cAMP-dependent phosphorylation in the Triton-extracted sperm and thereby inhibits the process to convert the sliding of outer doublet microtubules into the bending of the flagellum.