3.6.5.3	GTP + H2O = GDP + phosphate	this enzyme comprises a family of proteins involved in prokaryotic as well as eukaryotic protein synthesis. In the initiation factor complex, it is IF-2b (98kDa) that binds GTP and subsequently hydrolyses it in prokaryotes. in eukaryotes, it is eIF-2 (150 kDa) that binds GTP. In the elongation phase, the GTP-hydrolysing proteins are the EF-Tu polypeptide of the prokaryotic transfer factor (43 kDa), the eukaryotic elongation factor EF-1a (53 kDa), the prokaryotic EF-G (77 kDa), the eukaryotic EF-2 (70-110 kDa) and the signal recognition particle that play a role in endoplasmic reticulum protein synthesis (325 kDa). EF-Tu and EF-1a catalyse binding of aminoacyl-tRNA to the ribosomal A-site, while EF-G and EF-2 catalyse the translocation of peptidyl-tRNA from the A-side to the P-side. GTPase activity is also involved in polypeptide release from the ribosome with the aid of the pRFs and eRFs	
3.6.5.3	GTP + H2O = GDP + phosphate	reaction mechanism, overview	
3.6.5.3	GTP + H2O = GDP + phosphate	catalytic mechanism, structure-function relationship, overview	
3.6.5.3	GTP + H2O = GDP + phosphate	conformational changes of the protein upon nucleotide binding, in particular in the P-loop region, which extend to the functionally relevant switch II region. The latter carries a catalytically important and conserved histidine residue which is observed in different conformations in the GTP and GDP complexes. Activation of GTP hydrolysis may occur by a conformational repositioning of the histidine residue