cd03697

EFTU_II: Elongation factor Tu domain II. Elongation factors Tu (EF-Tu) are three-domain GTPases with an essential function in the elongation phase of mRNA translation. The GTPase center of EF-Tu is in the N-terminal domain (domain I), also known as the catalytic or G-domain. The G-domain is composed of about 200 amino acid residues, arranged into a predominantly parallel six-stranded beta-sheet core surrounded by seven a-helices. Non-catalytic domains II and III are beta-barrels of seven and six, respectively, antiparallel beta-strands that share an extended interface. Either non-catalytic domain is composed of about 100 amino acid residues. EF-Tu proteins exist in two principal conformations: in a compact one, EF-Tu*GTP, with tight interfaces between all three domains and a high affinity for aminoacyl-tRNA, and in an open one, EF-Tu*GDP, with essentially no G-domain-domain II interactions and a low affinity for aminoacyl-tRNA. EF-Tu has approximately a 100-fold higher affinity for GDP than for GTP.