Sulfhydryl groups are involved in the activation of sea urchin eggs.
Unfertilized sea urchin eggs exposed to the sulfhydryl reagents Ag+ or N-ethylmaleimide either elevated fertilizationlike membranes, formed surface protrusions, developed a clear cortical layer devoid of organelles, or cytolysed. The relative fraction of each modification varied from batch to batch and was also dose and time dependent. With Ag+ and higher doses of N-EMI (10(-3) M), the most common effect was the elevation of a membrane indicating cortical exocytosis, while at lower doses of N-EMI protrusions were predominant. Glutathione (GSH) protected eggs against these reagents also in a dose-dependent manner. Eggs exposed to equimolar amounts of N-EMI and GSH, which otherwise formed membranes, produced protrusions, while increasing GSH tenfold afforded complete protection. We suggest there are two targets for the sulfhydryl reagents--the first, SH groups on proteins that regulate the release of Ca2+ from the intracellular sequestering mechanism which subsequently triggers cortical exocytosis; the second, SH groups on the egg surface that may regulate cortical organization.
Dale
B
B
Stazione Zoologica, Villa Comunale, Naples, Italy.
Russo
P
P
D000818:Animals; D005260:Female; D008854:Microscopy, Electron; D010063:Ovum / Q000187:drug effects* / Q000648:ultrastructure; D012617:Sea Urchins / Q000502:physiology; D013438:Sulfhydryl Compounds / Q000494:pharmacology*
D013438:Sulfhydryl Compounds