Identification of GTP-Binding Proteins by ADP-Ribosylation in the Presence of Cholera Toxin, Pertussis Toxin and Botulinum Toxin D in Plasma Membrane Isolated from Eggs and Embryos of Sea Urchin.

Abstract

In plasma membrane fraction isolated from eggs and embryos of sea urchin, 32 P-labeled proteins were found on the fluorographs of SDS-polyacrylamide gel electrophoresis, performed after an exposure of the fraction to [adenylate-32 P] nicotinamide adenine dinucleotide in the presence of cholera toxin, pertussis toxin or botulinum toxin D. The molecular weights of proteins, thus ADP-ribosylated in the presence of cholera toxin and pertussis toxin are 45 and 39 K, which correspond to Gs and Gi or Go, respectively. Protein with the molecular weight of 24 K, labeled in the presence of botulinum toxin D, corresponds to small molecular weight G-protein. The labeling intensity of 45 K protein, probably proportional to its amount, became high at the blastula stage. The labeling intensity of 39 K protein was hardly altered up to the blastula stage. The labeling intensity of 24 K protein increased after fertilization and further increase occurred at the blastula stage. At the gastrula stage, the labeling intensities of these proteins became somewhat lower than at the blastula stage. Transmembrane signaling system, in which these G-proteins are involved, is probably altered in its function during early development.