Guanosine triphosphate binding sites

Achyuthan KE, Greenberg CS. Identification of a guanosine triphosphate-binding site on guinea pig liver transglutaminase. Role of GTP and calcium ions in modulating activity. J. Biol. Chem. 1987 262 1901-1906. 

The presence of a nitrogen-containing side chain facilitates interaction with the catalytic site of FPPS, an enzyme in the metabolic pathway that is required for the production of the isoprenoid hpids farnesyl diphosphate and geranylgeranyl diphosphate, essential metabolites for posttranslational protein prenylation [5, 8]. Inhibiting the prenylation of guanosine triphosphate-binding proteins such as Ras, Rho, and Rac disrupts the normal cellular signal transduction that is required for osteoclast function and survival [5]. 

The GDP is replaced at the nucleotide-binding site by guanosine triphosphate (GTP), which is present in a three to fourfold excess (50-300 u. I) in the cytosol. 

The evolution of protein structures shows conservation in recognition features for common binding sites. For example, the adenosine triphosphate (ATP)/ guanosine triphosphate (GTP) binding site contains an amino acid motif A (P-... 

The muscarinic cholinergic system has quite a different mode of operation in that the receptor is connected to the final action by a chain of events. Thus its response is slower than the nicotinic, where the receptor and ion channel are closely connected. Five distinct muscarinic receptors have been identified in mammals, based on anatomical location, genetic analysis, function, and amino acid sequence. All of them have seven transmembrane domains [166, 167, 168, 169]. The N- terminal domain outside the cell binds acetylcholine or other ligands at a site that includes an aspartate residue, while the C-terminal domain inside the cell is coupled to a so-called G-protein , which is initially bound to guanosine diphosphate (GDP), but exchanges it for guanosine triphosphate (GTP) when activated by its transmitter. The activated G-protein then activates phospholipase C, which hydrolyzes phosphoinositides to release 1,4,5-inositol triphosphate [170]. The final action depends on which type of cell is involved so that in some types ion channels are opened just as with the nicotinic receptor, but in other cases other processes are affected, for example the release of dopamine [171]. Since there are these differences... 

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