These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Inhibition of the GTPase activity of transducin by an NAD+:arginine ADP-ribosyltransferase from turkey erythrocytes.
    Author: Watkins PA, Kanaho Y, Moss J.
    Journal: Biochem J; 1987 Dec 15; 248(3):749-54. PubMed ID: 2829839.
    Abstract:
    The bacterial toxins, choleragen and pertussis toxin, inhibit the light-stimulated GTPase activity of bovine retinal rod outer segments by catalysing the ADP-ribosylation of the alpha-subunit (T alpha) of transducin [Abood, Hurley, Pappone, Bourne & Stryer (1982) J. Biol. Chem. 257, 10540-10543; Van Dop, Yamanaka, Steinberg, Sekura, Manclark, Stryer & Bourne (1984) J. Biol. Chem. 259, 23-26]. Incubation of retinal rod outer segments with NAD+ and a purified NAD+:arginine ADP-ribosyltransferase from turkey erythrocytes resulted in approx. 60% inhibition of GTPase activity. Inhibition was dependent on both enzyme and NAD+, and was potentiated by the non-hydrolysable GTP analogues guanosine 5'-[beta gamma-imido]triphosphate (p[NH]ppG) and guanosine 5'-[beta gamma-methylene]triphosphate (p[CH2]ppG). The transferase ADP-ribosylated both the T alpha and T beta subunits of purified transducin. T alpha (39 kDa), after ADP-ribosylation, migrated as two distinct peptides with molecular masses of 42 kDa and 46 kDa on SDS/polyacrylamide-gel electrophoresis. T beta (36 kDa), after ADP-ribosylation, migrated as a 38 kDa peptide. With purified transducin subunits, it was observed that the GTPase activity of ADP-ribosylated T alpha, reconstituted with unmodified T beta gamma and photolysed rhodopsin, was decreased by 80%; conversely, reconstitution of T alpha with ADP-ribosyl-T beta gamma resulted in only a 19% inhibition of GTPase. Thus ADP-ribosylation of T alpha, the transducin subunit that contains the guanine nucleotide-binding site, has more dramatic effects on GTPase activity than does modification of the critical 'helper subunits' T beta gamma. To elucidate the mechanism of GTPase inhibition by transferase, we studied the effect of ADP-ribosylation on p[NH]pp[3H]G binding to transducin. It was shown previously that modification of transducin by choleragen, which like transferase ADP-ribosylates arginine residues, did not affect guanine nucleotide binding. ADP-ribosylation by the transferase, however, decreased p[NH]pp[3H]G binding, consistent with the hypothesis that choleragen and transferase inhibit GTPase by different mechanisms.
    [Abstract] [Full Text] [Related] [New Search]