IDENTIFICATION OF FLAGELLAR PROTEINS THAT INITIATE THE ACTIVATION OF SPERM MOTILITY IN-VIVO

Protein phosphorylation appears to be a necessary step in the intracel lular signaling pathway that initiates the activation of sperm motilit y. Activation of live immotile sea urchin sperm produced rapid, time-d ependent increased phosphorylation on proteins of 32, 45, 130, and 500 kDa. Fractionation of immotile and motile sperm indicated that these motility-related phosphoproteins are associated with flagella. These p roteins showed greater phosphorylation in the flagellar fraction from motile sperm, suggesting that subcellular boundaries are in place to k eep protein kinases and their substrates spatially separated, Solubili ty properties suggest that these proteins are the heavy chain and smal ler subunits of sea urchin sperm dynein which are phosphorylated in vi vo to initiate activation of motility, This also suggests that phospho rylation of only these few proteins, out of the nearly 100 phosphoryla tions known to occur in the basic axoneme, appears to be associated wi th the early signaling pathways of motility activation in intact sperm . (C) 1998 Academic Press.