Structure and Function of Egg-Associated Peptides of Sea Urchins

Abstract

The sea urchin egg is surrounded by a gelatinous extracellular matrix called the jelly coat through which spermatozoa must pass before reaching the plasma membrane of the egg during fertilization (Fig.1). Lillie (1913) observed that the jelly coat, dissolved in sea water, is able to cause a transitory activation of sperm motility and sperm agglutination. Thereafter, many investigators have shown that soluble factors associated with sea urchin eggs stimulate the motility and respiration of sea urchin spermatozoa (Carter, 1931; Cohn, 1918; Gray, 1928; Rothschild, 1956a, 1956b). Hathaway (1963) reported that the factors are diffusible in dialysis, heat-stable, alcohol-soluble and non-volatile. Ohtake (1976a, 1976b) demonstrated that the respiration of sea urchin spermatozoa could be reproducibly stimulated by partially purified egg jelly factors obtained from the sea urchin Pseudocentrotus depressus if extracellular pH was maintained at acidic values. Kopf et al (1979) and Hansbrough and Garbers (1981a) then found that the egg jelly of the sea urchin Strongylocentrotus purpuratus contains a factor which elevates the respiratory rate and cyclic AMP and cyclic GMP concentrations of S. purpuratus spermatozoa. Suzuki and co-workers (1981) have purified from the egg jelly of the sea urchin Hemicentrotus pulcherrimus a decapeptide able to stimulate sperm respiration whose sequence is Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly.