THE SEA-URCHIN EXTRAEMBRYONIC HYALINE LAYER - IONIC PARAMETERS CONTROLLING THE HYALIN GELATION REACTION

1. 1. As reported previously (Robinson, 1988) the Ca2+-induced self-association reaction of the protein hyalin, purified from the sea urchin extraembryonic hyaline layer, was modulated by both Mg2+ and NaCl. 2. 2. In the presence of 400 mM NaCl the apparent dissociation constant (Ca2+) decreased five-fold from 4.8 ± 1.1 mM in the absence to 0.9 ± 0.5 mM in the presence of 20 mM Mg2+. 3. 3. The potentiating effect of Mg2+ occurred with an apparent dissociation constant (Mg2+) of 4.6 ± 0.5mM. 4. 4. In the absence of Ca2+ or NaCl hyalin dissociated from isolated hyaline layers indicating that the behavior of hyalin within the layer is predictable from results obtained with the purified protein. © 1990.