EVIDENCE FOR THE PROTEIN NATURE OF THE SPERM AGGLUTININS OF THE KEYHOLE LIMPET AND THE SEA-URCHIN

¹ From the William G. Kerckhoff Laboratories of the Biological Sciences, California Institute of Technology, Pasadena

Some of the chemical and physical properties of the sperm agglutinin (fertilizin) of the keyhole limpet Megathura crenulata and of the sea-urchin Strongylocentrotus purpuratus were investigated. In both species the agglutinins were found to be non-dialyzable. They precipitate completely without loss of activity in nearly saturated ammonium sulfate. They are adsorbed by CaCO₃, Al_2O3, charcoal and kaolin. The agglutinins are insoluble in alcohol and ether. Active concentrates give, contrary to the findings of earlier investigators, the common color tests for proteins and are found to contain nitrogen. Solutions of crystallized proteinases (trypsin and chymotrypsin) inactivate the agglutinins. They are also inactivated by heat as a function of pH. From the evidence it is concluded that in both species the agglutinating principle is either protein or very closely associated with protein.

The keyhole limpet agglutinin is much more resistant than is that of the sea-urchin to inactivation by heat and by proteolytic enzymes. It is suggested that the difference between the two species in the duration of the agglutination reaction may be related to the difference in stability of the respective agglutinins.