ADP-ribosylation of transducin by islet-activation protein. Identification of asparagine as the site of ADP-ribosylation.

作者：David R. Manning, Blair A. Fraser, Richard Kahn, Alfred G. Gilman · 发表于：Journal of Biological Chemistry · 年份：1984 · DOI：10.1016/s0021-9258(17)43521-6 · 被引用次数：138 · 研究领域：PARP inhibition in cancer therapy、Cardiac electrophysiology and arrhythmias、Receptor Mechanisms and Signaling

Islet-activating protein catalyzes the ADP-ribosylation of transducin, a guanine nucleotide-binding regulatory protein that mediates activation of a retinal cyclic GMP-selective phosphodiesterase. Radiolabel from [adenylate-32P]NAD+ was incorporated specifically into the alpha subunit of purified transducin. Maximal levels of incorporation approximated 0.8 mol of ADP-ribose/mol of transducin. A peptide containing the ADP-ribosyl moiety was purified from a tryptic digest of radiolabeled transducin. This peptide was characterized by chemical and enzymatic procedures and by fast atom bombardment mass spectrometry. The primary structure of this peptide was Glu-Asn-Leu-Lys-Asn(ADP-ribose)-Gly-Leu-Phe. It is probable that the peptide originated from the carboxyl terminus of the alpha subunit and that the ADP-ribosyl moiety is attached by an N-glycosidic linkage to the asparagine residue. Transducin associated with retinal disc membranes is also ADP-ribosylated by cholera toxin. Cholera toxin and islet-activating protein sequentially catalyze the incorporation of 1.9 mol of ADP-ribose/mol of transducin, indicating two distinct sites of ADP-ribosylation within transducin.