Interaction of ADP-ribosylation factor with Escherichia coli enterotoxin that contains an inactivating lysine 112 substitution.

摘要: Cholera toxin and Escherichia coli heat-labile enterotoxin (LT) exert their effects on cells through ADP-ribosylation of guanine nucleotide-binding proteins. Both toxins consist one A subunit, which is an ADP-ribosyltransferase, five B (or binding) subunits. Their enzymatic activities are latent; activation requires reduction proteolysis, resulting in a catalytically active A1 protein much smaller A2 protein. These ADP-ribosyltransferases activated by GTP-dependent 20-kDa factors or ARFs. To determine if proteolysis plus required for appearance the ARF allosteric site as well catalytic activity, inactive mutant LT, LT(E112K), with replacement glutamate lysine at position 112 its was utilized competitor cholera ADP-ribosyltransferase assays containing limiting amounts ARF. LT(E112K) trypsinization to become potent, concentration-dependent inhibitor. Inhibition reversed increasing concentrations Reduction alone did not generate inhibitory form LT(E112K). studies consistent conclusion that expressed latent toxin. expression functional binding activity.