GTP-binding proteins and their regulatory actions on ion channels.

Sato, Makoto

doi:10.2170/jjphysiol.39.461

Cited by 9 publications

(3 citation statements)

References 70 publications

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“…It now appears, however, that the ply subunits may have additional or other roles, including regulation ofthe activated a subunit (1)(2)(3)(4)(5) and modulation of such effectors as ion channels (7)(8)(9)(10) and the enzymes phospholipase A2 and adenylyl cyclase (11)(12)(13)(14). Nonetheless, the diversities of the ,( and 'y subunits are still believed to be much less than that of the a subunit.…”

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confidence: 99%

Retinal rods and cones have distinct G protein beta and gamma subunits.

Peng

Robishaw

Levine

et al. 1992

Proc. Natl. Acad. Sci. U.S.A.

136

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Guanine nucleotide-binding proteins (G proteins) involved in transmembrane signal-transduction processes are heterotrimers composed of a, 13, and y subunits. The a subunit shows great diversity and is thought to confer functional specificity to a particular G protein. By contrast, the 13 and y subunits appear much less diverse; in particular, the 13 subunit is believed to have no role in G protein specificity. Using immunocytochemistry, we found distinct distribution patterns for different 13 and y subunits in the retina. In particular, rod and cone photoreceptors, which both subserve phototransduction but differ in light-response properties, have different 13 and y subunits in their outer segments. Thus, the G protein mediating phototransduction shows cell-specific forms of the 13 and y subunits in addition to the a subunit. This surprising finding supports the hypothesis that these subunits may also contribute to functional specificity of a G protein.The family of guanine nucleotide-binding proteins (G proteins) mediates a wide variety of cellular signal-transduction processes triggered by hormones, neurotransmitters, and sensory stimuli (for review, see refs. 1-5). Structurally these proteins are heterotrimers, consisting of a, (3, and y subunits.The functional diversity of these proteins is thought to derive primarily from the a subunit, of which at least 16 species have been identified, based on biochemical purification or molecular cloning (4, 5). Their functions range from activation or inhibition of various enzymes-such as adenylate cyclase, cGMP phosphodiesterase, and phospholipase C-to modulation of ion channels. Less is known about ( and y subunits. These subunits are tightly bound to each other to form a complex and are only separable under denaturing conditions. The fry complex was initially thought to anchor the a subunit to the membrane, thereby facilitating its interaction with the receptor (6). It now appears, however, that the ply subunits may have additional or other roles, including regulation ofthe activated a subunit (1-5) and modulation of such effectors as ion channels (7-10) and the enzymes phospholipase A2 and adenylyl cyclase (11)(12)(13)(14). Nonetheless, the diversities of the ,( and 'y subunits are still believed to be much less than that of the a subunit. Thus, fBy complexes appear relatively interchangeable among different G proteins (15,16). Some differences in properties between different fry complexes have been noticed and have been attributed largely to the 'y subunit (17, 18), for which six species with a molecular size of 6-10 kDa have been identified (4,5,(19)(20)(21)(22). Biochemical studies have identified only two forms of P subunit; these have been designated P35 and (36 based on their apparent molecular masses of 35 and 36 kDa in gel electrophoresis (23)(24)(25)(26)(27)(28). Subsequent molecular cloning has indicated that (35 and P36 subunits correspond to closely homologous, but distinct, proteins designated (32 and (, (29-34). More recently, however, a third ...

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mentioning

confidence: 99%

Retinal rods and cones have distinct G protein beta and gamma subunits.

Peng

Robishaw

Levine

et al. 1992

Proc. Natl. Acad. Sci. U.S.A.

136

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“…Nonhydrolysable GTP-analogues such as guanosine-5'-(3-O-thio)triphosphate (GTPrs) and guanosine 5'-(P, y-imin0)triphosphate (Gpp(NH)p), therefore, can 'switch on' the G-protein activation irreversibly without causing 'switch off' (Sato, 1989). Hitherto, briefly, in the basal state, Gproteins exist in their oligomeric form with guanosine diphosphate (GDP) tightly bound to the catalytic site of guanosine triphosphatase (GTPase) localized in the a-subunit of G-proteins such as Gs.…”

Section: Interactions Among P-adrenoceptors G-proteins and Adenylyl mentioning

confidence: 99%

“…This activation can be 'switched off' when hydrolysed GDP re-occupies the catalytic site, and a-subunit reassociates with P-y-subunit to form stable conformation of Gs. Nonhydrolysable GTP-analogues such as guanosine-5'-(3-O-thio)triphosphate (GTPrs) and guanosine 5'-(P, y-imin0)triphosphate (Gpp(NH)p), therefore, can 'switch on' the G-protein activation irreversibly without causing 'switch off' (Sato, 1989).…”

Section: Interactions Among P-adrenoceptors G-proteins and Adenylyl mentioning

confidence: 99%