Biomaterial Database

Characterization of transducin from bovine retinal rod outer segments. The role of sulfhydryl groups. 1984

Y K Ho, and B K Fung

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 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 alpha subunit of transducin contained three accessible sulfhydryl groups under both native and 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 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 alpha -Gpp(NH)p inhibited the exchange of the bound Gpp(NH)p for GTP. However, the modified T 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 alpha occurs upon the binding of Gpp(NH)p and a specific sulfhydryl group of T alpha plays an important role in the activation of transducin in retinal rod outer segments.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008565	Membrane Proteins	Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.	Cell Membrane Protein,Cell Membrane Proteins,Cell Surface Protein,Cell Surface Proteins,Integral Membrane Proteins,Membrane-Associated Protein,Surface Protein,Surface Proteins,Integral Membrane Protein,Membrane Protein,Membrane-Associated Proteins,Membrane Associated Protein,Membrane Associated Proteins,Membrane Protein, Cell,Membrane Protein, Integral,Membrane Proteins, Integral,Protein, Cell Membrane,Protein, Cell Surface,Protein, Integral Membrane,Protein, Membrane,Protein, Membrane-Associated,Protein, Surface,Proteins, Cell Membrane,Proteins, Cell Surface,Proteins, Integral Membrane,Proteins, Membrane,Proteins, Membrane-Associated,Proteins, Surface,Surface Protein, Cell
D009579	Nitrobenzoates	Benzoic acid or benzoic acid esters substituted with one or more nitro groups.	Nitrobenzoic Acids,Acids, Nitrobenzoic
D010786	Photoreceptor Cells	Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade.	Ciliary Photoreceptor Cells,Ciliary Photoreceptors,Rhabdomeric Photoreceptor Cells,Rhabdomeric Photoreceptors,Cell, Ciliary Photoreceptor,Cell, Photoreceptor,Cell, Rhabdomeric Photoreceptor,Cells, Ciliary Photoreceptor,Cells, Photoreceptor,Cells, Rhabdomeric Photoreceptor,Ciliary Photoreceptor,Ciliary Photoreceptor Cell,Photoreceptor Cell,Photoreceptor Cell, Ciliary,Photoreceptor Cell, Rhabdomeric,Photoreceptor Cells, Ciliary,Photoreceptor Cells, Rhabdomeric,Photoreceptor, Ciliary,Photoreceptor, Rhabdomeric,Photoreceptors, Ciliary,Photoreceptors, Rhabdomeric,Rhabdomeric Photoreceptor,Rhabdomeric Photoreceptor Cell
D002417	Cattle	Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.	Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D004228	Dithionitrobenzoic Acid	A standard reagent for the determination of reactive sulfhydryl groups by absorbance measurements. It is used primarily for the determination of sulfhydryl and disulfide groups in proteins. The color produced is due to the formation of a thio anion, 3-carboxyl-4-nitrothiophenolate.	5,5'-Dithiobis(2-nitrobenzoic Acid),DTNB,Ellman's Reagent,5,5'-Dithiobis(nitrobenzoate),Acid, Dithionitrobenzoic,Ellman Reagent,Ellmans Reagent,Reagent, Ellman's
D005033	Ethylmaleimide	A sulfhydryl reagent that is widely used in experimental biochemical studies.	N-Ethylmaleimide,N Ethylmaleimide
D006160	Guanosine Triphosphate	Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.	GTP,Triphosphate, Guanosine
D006165	Guanylyl Imidodiphosphate	A non-hydrolyzable analog of GTP, in which the oxygen atom bridging the beta to the gamma phosphate is replaced by a nitrogen atom. It binds tightly to G-protein in the presence of Mg2+. The nucleotide is a potent stimulator of ADENYLYL CYCLASES.	GMP-PNP,GMP-P(NH)P,Gpp(NH)p,Guanosine 5'-(Beta,Gamma-Imido)Triphosphate,Guanyl-5'-Imidodiphosphate,P(NH)PPG,Guanyl 5' Imidodiphosphate,Imidodiphosphate, Guanylyl
D000596	Amino Acids	Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.	Amino Acid,Acid, Amino,Acids, Amino