Guanine nucleotide-binding protein in sea urchin eggs serving as the specific substrate of islet-activating protein, pertussis toxin |
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Authors: | M Oinuma T Katada H Yokosawa M Ui |
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Affiliation: | 1. >Department of Physiological Chemistry, Hokkaido University, Sapporo 060, Japan;2. Department of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060, Japan |
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Abstract: | A GTP-binding protein serving as the specific substrate of islet-activating protein (IAP), pertussis toxin, was partially purified from Lubrol extract of sea urchin egg membranes. The partially purified protein possessed two polypeptides of 39 and 37 kDa; the 39 kDa polypeptide was specifically ADP-ribosylated by IAP and the 37 kDa protein cross-reacted with the antibody prepared against purified beta gamma-subunits of alpha beta gamma-heterotrimeric IAP substrates from rat brain. Incubation of this sea urchin IAP substrate with a non-hydrolyzable GTP analogue resulted in a reduction of the apparent molecular mass on a column of gel filtration as had been the case with purified rat brain IAP substrates, suggesting that the sea urchin IAP substrate was also a heterooligomer dissociable into two polypeptides in the presence of GTP analogues. Thus, the 39 and 37 kDa polypeptides of the sea urchin IAP substrate correspond to the alpha- and beta-subunits, respectively, of mammalian IAP substrates which are involved in the coupling between membrane receptor and effector systems. |
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