Guanyl nucleotides

Battaglia, G. Shannon, M. and Titeler. M. Guanyl nucleotide and divalent cation regulation of cortical S2 serotonin receptors. J Neurochem 43 1213-1219, 1984. 

Microtubules have a key role in mitosis and cell-proliferation. They are dynamic assemblies of heterodimers of a and f3 tubullin. In the cell-reproduction cascade tubulin polymerizes fast and subsequently depolymerizes. Tubulin dimers are unusual guanyl nucleotide binding (G) proteins, which bind GTP reversibly at a site in the (3-tubulin. GTP irreversibly hydrolyzes to GDP during polymerization. 

Ratomponirina, C., Hode, Y., Hechler, V., and Maitre, M. (1995) Gamma-hydroxybutyrate receptor binding in rat brain is inhibited by guanyl nucleotides and pertussis toxin. Neuro sci. Lett. 189, 51-53. 

Ebinn, J.O., Bottorf, D.A., Chan, E.Y.W., Stang, S.L., Dunn, R.J. and Stone, J.C. RasGRP, a ras guanyl nucleotide-releasing protein with calcium- and diacylglycerol-binding motifs (1998) Science 280,1082-1086... 

This toxin subunit is an enzyme, an ADP-ribo-syltransferase which catalyzes transfer of ADP-ribosyl units from the coenzyme NAD+ to specific arginine side chains to form N-ADP-ribosyl derivatives of various proteins. Of the proteins modified by cholera toxin, the most significant is the guanyl nucleotide regulatory protein Gs of the adenylate cyclase system.C/f/h ADP ribosylation of arginine 201 of the a subunit of protein Gs inhibits the GTP hydrolysis that normally allows the protein to relax to an unactivated form.e The ADP-ribosylated Gs keeps adenylate cyclase activated continuously and... 

Initial biochemical studies indicate that agonist binding was regulated by guanyl nucleotides, implying that the receptor belongs to the superfamily of receptors coupled to G proteins. In addition, various intracellular responses were found to be associated with Hi-receptor stimulation inositol phosphate release, increase in Ca2+ fluxes, cyclic AMP or cyclic GMP accumulation in whole cells and arachidonic acid release [1],... 

Hill DR, Bowery NG, Hudson AL (1984) Inhibition of GABAb receptor binding by guanyl nucleotides. J Neurochem 42 652-7... 

As Illustrated in Fig. 7, 3 yM CRF and 1 yM (-)Isoproterenol cause a 190 and 110% stimulation of adenylate cyclase activity In rat pars intermedia particulate fraction, respectively. An additive effect Is observed when both stimulatory agents are present. Dopamine (30 yM), on the other hand, has no significant effect alone. However, In the presence of GXP, the catecholamine causes a 40 to 60% Inhibition of adenylate cyclase activity stimulated by CRF, ISO or CRF + ISO. It can also be seen that while 0.3 mM GXP alone causes a 100% increase In basal adenylate cyclase activity, it leads to a marked potentiation of the effect of ISO and CRF on [ 2P] cyclic AMP accumulation. It should be noticed that In the absence of the guanyl nucleotide, dopamine has no Inhibitory effect on adenylate cyclase activity In any of the groups studied. 

As mentioned earlier, guanyl nucleotides have been found to play an important role In the activation of adenylate cyclase activity by many hormones (90, 91). The present observations show that in pars Intermedia tissue, GXP causes an almost doubling of the stimulatory effect of CRF while that of the B-adrenerglc ago-... 

Lyon RA, Davis KH, Titeler M. 3H-DOB (4-bromo-2,5-dimethoxyphenyl-isopropylamine) labels a guanyl nucleotide-sensitive state of cortical 5-HT2 receptors. Mol Pharmacol 1987 31 194-199. 

Adenylate cyclase is a two-component enzyme system. It ultimately catalyzes the cyclase reaction, but only when it is associated with the hormone-bound receptor and a regulatory protein called a stimulatory G-protein (guanylate nucleotide binding protein), which activates adenylate cyclase. The G-protein is the intermediate between the receptor and the synthesis of cyclic AMP. 

G-proteins exist either in an active or an inactive state, depending on the guanylate nucleotide that is bound. In the inactive state, G-protein binds to GDP. In the active state, GTP is bound to the G-pro-tein. G-proteins have an intrinsic GTPase activity, which converts bound GTP to GDP. Hydrolysis of GTP by the G-protein converts the G-protein back to an inactive state. Thus the cycle of the G-protein is as follows ... 

Snyder SH, Childers SR, Creese I. Molecular actions of opiates historical overview and new findings on opiate receptor interactions with enkephalins and guanyl nucleotides. Adv Biochem Psychopharmacol 1979 20 543-552. 

G alpha(q) (Guanyl Nucleotide Binding Protein G Alpha q)... 

Perrin MH, Haas Y, Rivier JE, Vale WW (1986) Corticotropinreleasing factor binding to the anterior pituitary receptor is modulated by divalent cations and guanyl nucleotides. Endocrinology 118 1171-9... 

G protein, heterotrimeric guanyl nucleotide-binding protein... 

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