Characterization of transducin from bovine retinal rod outer segments: the role of sulfhydrye groups

Journal Article · Fri May 25 00:00:00 EDT 1984 · J. Biol. Chem.; (United States)

OSTI ID:6105432

Fung, B K.K.

The properties and functions of the sulfhydryl groups of transducin were examined by 5,5'-dithiobis-(2-nitrobenzoic acid) titration and N-ethylmaleimide modification. The T/sub ..beta gamma../ subunit of transducin contained a total of six free sulfhydryl groups and two were reactive under native conditions. Both reactive sulfhydryl groups were located in the ..beta.. polypeptide. The functions of transducin were not affected by the modification of these two sulfhydryl groups. The T/sub ..cap alpha../ subunit of transducin contained three accessible sulfhydryl groups under both native aqnd denaturing conditions. When 1.3 sulfhydryl groups were covalently modified by N-ethylmaleimide, the GTPase activity, the guanosine 5'-(..beta..,..gamma..-imido)triphosphate (Gpp(NH)p) uptake, and the rhodopsin-binding property of transducin were inhibited. The binding of Gpp(NH)p to T/sub ..cap alpha../ blocked two of the three sulfhydryl groups from chemical modification and increased the reactivity of the remaining one. Modification of this specific sulfhydryl group of T/sub ..cap alpha../-Gpp(NH)p inhibited the exchange of the bound Gpp(NH)p for GTP. However, the modified T/sub ..cap alpha../-Gpp(NH)p was able to activate cGMP phosphodiesterase in solution and on positively charged liposomes. These findings demonstrated that a conformational change of T/sub ..cap alpha../ occurs upon the binding of Gpp(NH)p and a specific sulfhydryl group of T/sub ..cap alpha../ plays an important role in the activation of transducin in retinal rod outer segments. 31 references, 6 figures, 1 table.

• Research Organization: Univ. of Rochester, NY
• OSTI ID: 6105432
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 259:10; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BIOCHEMICAL REACTION KINETICS
BODY
BODY AREAS
CATTLE
CELL CONSTITUENTS
COVALENCE
DATA
DOMESTIC ANIMALS
ENZYMES
ESTERASES
EXPERIMENTAL DATA
EYES
FACE
HEAD
HYDROLASES
INFORMATION
KINETICS
LIPOSOMES
MAMMALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
PEPTIDES
PHOSPHODIESTERASES
PIGMENTS
POLYPEPTIDES
PROTEINS
PURIFICATION
REACTION KINETICS
RETINA
RHODOPSIN
RUMINANTS
SENSE ORGANS
VERTEBRATES