Roles for Ca2+, Mg2+ and NaCl in modulating the self-association reaction of hyalin, a major protein component of the sea-urchin extraembryonic hyaline layer.
The self-association reaction of hyalin, a major protein component of the sea-urchin extraembryonic hyaline layer, was examined. Concentrations of Ca2+ below 1 mM had little effect on the hyalin gelation reaction, but higher concentrations of the cation induced protein aggregation. Quantitative aggregate formation required a Ca2+ concentration in excess of 10 mM. This reaction was modulated by both NaCl and Mg2+. The effectiveness of Ca2+ in inducing hyalin gelation was markedly enhanced in the presence of 500 mM-NaCl, the concentration found in sea water. Similarly, 20 mM-Mg2+ also enhanced Ca2+-induced hyalin gelation. Neither NaCl nor Mg2+ alone induced hyalin gelation. Concentrations of Ca2+ as low as 1 mM effectively protected hyalin from tryptic digestion both in the presence and in the absence of 500 mM-NaCl. The latter result suggested that, although higher concentrations of Ca2+ were required to induce the hyalin gelation reaction, lower concentrations of the cation could mediate a protein-protein interaction in an NaCl-independent fashion. These results identify the parameters that modulate hyalin self-association, a reaction that is essential for hyaline-layer assembly around the developing sea-urchin embryo.
Robinson
J J
JJ
Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D004357:Drug Synergism; D004591:Electrophoresis, Polyacrylamide Gel; D006818:Hyalin / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008274:Magnesium / Q000494:pharmacology*; D008954:Models, Biological; D010063:Ovum / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D012617:Sea Urchins; D012965:Sodium Chloride / Q000494:pharmacology*
D046911:Macromolecular Substances; D010446:Peptide Fragments; D012965:Sodium Chloride; D008274:Magnesium; D002118:Calcium