ADP-ribosylation of transducin by pertussis toxin
Transducin, the guanyl nucleotide-binding regulatory protein of retinal rod outer segments that couples the photon receptor, rhodopsin, with the light-activated cGMP phosphodiesterase, can be resolved into two functional components, T alpha and T beta gamma. T alpha (39 kDa), which is (TSP)ADP-ribosylated by pertussis toxin and (TSP)NAD in rod outer segments and in purified transducin, was also labeled by the toxin after separation from T beta gamma (36 kDa and approximately 10 kDa); neither component of T beta gamma was a pertussis toxin substrate. Labeling of T alpha was enhanced by T beta gamma and was maximal at approximately 1:1 molar ratio of T alpha : T beta gamma. Limited proteolysis by trypsin of T alpha in the presence of guanyl-5'-yl imidodiphosphate (Gpp(NH)p) resulted in the sequential appearance of proteins of 38 and TS kDa. The amino terminus of both 38- and TS-kDa proteins was leucine, whereas that of T alpha could not be identified and was assumed to be blocked. The TS-kDa peptide was not a pertussis toxin substrate. Labeling of the 38-kDa protein was poor and was not enhanced by T beta gamma. Trypsin treatment of (TSP)ADP-ribosyl-T alpha produced a labeled 37-38-kDa doublet followed by appearance of radioactivity at the dye front. It appears, therefore, that, although the 38-kDa protein was poor toxin substrate, it contained the ADP-ribosylation site. Without rhodopsin, labeling of T alpha (in the presence of T beta gamma) was unaffected by Gpp(NH)p, guanosine 5'-O-(thiotriphosphate) (GTP gamma S), GTP, GDP, and guanosine 5'-O-(thiodiphosphate) (GDP beta S) but was increased by ATP. When photolyzed rhodopsin and T beta gamma were present, Gpp(NH)p and GTP gamma S decreased (TSP)ADP-ribosylation by pertussis toxin. Thus, pertussis toxin-catalyzed (TSP)ADP-ribosylation of T alpha was affected by nucleotides, rhodopsin and light in addition to T beta gamma.
- Research Organization:
- National Heart, Lung, and Blood Institute, Bethesda, MD
- OSTI ID:
- 6085100
- Journal Information:
- J. Biol. Chem.; (United States), Vol. 25
- Country of Publication:
- United States
- Language:
- English
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PROTEINS
LABELLING
METABOLISM
TRYPSIN
PROTEOLYSIS
ADP
CATALYSTS
INFECTIOUS DISEASES
LEUCINE
NAD
NUCLEOTIDES
PHOSPHATES
PHOSPHORUS 32
RHODOPSIN
RIBOSE
TOXINS
TRACER TECHNIQUES
VISIBLE RADIATION
ALDEHYDES
AMINO ACIDS
ANTIGENS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOHYDRATES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COENZYMES
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
DISEASES
ELECTROMAGNETIC RADIATION
ENZYMES
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MATERIALS
MONOSACCHARIDES
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PENTOSES
PEPTIDE HYDROLASES
PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
PIGMENTS
RADIATIONS
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SACCHARIDES
SERINE PROTEINASES
TOXIC MATERIALS
550501* - Metabolism- Tracer Techniques