GTPases domain

The GTPase domain ofGa binds to Gp in the heterotrimeric Gapy complex... 

Gq-GDP binds to the Gpy dimer through its GTPase domain in a region of the p propeller opposite to where G is bound (Figure 13.15). There are, therefore, no contacts between Gq and Gy in the heterotrimeric G py complex. The... 

Gt,a is made up of two domains, a GTPase domain and a helical domain. The GTPase or G-domain indicates that Gt, is a member of the superfamily of regulatory GTPases. In addition, G, possesses a helical domain, which represents a characteristic feature of the heterotrimeric G-proteins. The nucleotide binding site is in a cleft between the two domains. It is assumed that the presence of the helical domain is the reason that bound nucleotide dissociates only very slowly from transducin and that the activated receptor is therefore necessary to initiate the GDP/GTP exchange. 

EF-G binds to the 50S ribosomal subunit at the base of the L7 /12 stalk as indicated in Fig. 29-1 392/393 It competes with EF-Tu, which binds in nearly the same location.5 EF-G is a large five-domain GTPase. Domain 1 contains the GTPase site and resembles other G proteins, and domain 2 has some similarity to the... 

Structurally, each Ga subunit consists of two domains—a GTPase domain, and a a-helical domain. In between these two domains is a cleft where guanine nucleotide binds. Lipid modification of a Cys residue near the amino-terminus of the Ga subunit allows for binding to membrane [8], and the carboxyl terminus of the protein appears important for interaction with receptor. Indeed, the last five residues of Ga are believed to contribute to specificity of interaction [reviewed in 9]. However Ho and Wong [10] have demonstrated that the amino terminus of Gaz is also a critical determinant of its coupling to the delta opioid receptor. 

Damke, H., Binns, D. D., Ueda, H., Schmid, S. L., and Baba, T. (2001) Dynamin GTPase domain mutants block endocytic vesicle formation at morphologically distinct stages. Mol Biol Cell 12,2578-2589. 

Brenner TJ, Guthrie C. Assembly of Snull4 into U5 snRNP requires Prp8 and a functional GTPase domain. RNA 2006 12 862-871. 

To better understand how receptors and G proteins interact with each other at a molecular level, the regions on the G proteins with which the various intracellular receptor domains (see above) can functionally interact need to be identified. Biochemical studies suggest that at least three distinct regions on the GTPase domain of the G protein a-subunits, including the N- and the C-terminus, can directly contact the receptor [40,41]. These regions clearly differ from those predicted to be involved in the activation of effector enzymes such as adenylyl cyclase [42] or phospholipase C [43]. 

Ga t is made up of two domains, a GTPase domain and a helical domain. The GTPase or G-domain indicates that Ga t is a member of the superfamily of regulatory GTPases. In addition, Gat possesses a helical domain, which represents a characteristic feature of... 

The differences in the cycling mechanisms of Ras and G, are reflected In their structures. Ras ( 170 amino acids) is smaller than Gq, proteins ( 300 amino acids), but its three-dimensional structure Is similar to that of the GTPase domain of G, (see Figure 13-8). Recent structural and biochemical studies show that G, also contains another domain that apparently functions like GAP to increase the rate of GTP hydrolysis by Gc,. In addition, the direct interaction between an activated receptor and inactive G protein promotes release of GDP and binding of GTP, so that a separate nucleotide exchange factor is not required. 

Dynamin 1, a member of the dynamin family of large GTPases. Mammalian dynamin 1 forms ring-like assemblies aroimd the necks of budding synaptic vesicles. StmeturaUy, it can be subdivided into five domains. The high-resolution X-ray structure of the GTPase domain from Rattus norvegicus was described in 2005 [K. Takei et al.. Nature 1995, 374,186 ... 

Song, B. D., Leonard, M., and Schmid, S. L. (2004b). Dynamin GTPase domain mutants that differentially affect GTP binding, GTP hydrolysis, and clathrin-mediated endocytosis. /. Biol Chem. 279, 40431-40436. 

Dynamin comprises several functional domains. The GTPase domain of dynamin is located at its N-terminus and is followed by the pleckstrin... 

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