Mono ADP-ribosylation of transducin catalyzed by rod outer segment extract.
Transducin is the retinal rod outer segment (ROS)-specific G protein coupling the photoexcited rhodopsin to cyclic GMP-phosphodiesterase. The alpha subunit of transducin is known to be ADP-ribosylated by bacterial toxins. We investigated the possibility that transducin is modified in vitro by an endogenous ADP-ribosyltransferase activity. By using either ROS, cytosolic extract of ROS or purified transducin in the presence of [alpha-32P]nicotinamide adenine dinucleotide (NAD+), the alpha and beta subunits of transducin were found to be radiolabeled. The labeling was decreased by snake venom phosphodiesterase I (PDE I). The modification was shown to be mono ADP-ribosylation by analyses on thin layer chromatography of the PDE I-hydrolyzed products which revealed only 5'AMP residues. In addition we report that sodium nitroprusside activates the ADP-ribosylation of transducin.
Ehret-Hilberer
S
S
INSERM Unité 338, Strasbourg, France.
Nullans
G
G
Aunis
D
D
Virmaux
N
N
D000244:Adenosine Diphosphate / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D004591:Electrophoresis, Polyacrylamide Gel; D012266:Ribose / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D015293:Transducin / Q000378:metabolism*
D000244:Adenosine Diphosphate; D012266:Ribose; D015293:Transducin