3-DIMENSIONAL STRUCTURE OF THE RIBOSOMAL TRANSLOCASE - ELONGATION-FACTOR-G FROM THERMUS-THERMOPHILUS

The crystal structure of Thermus thermophilus elongation factor G with out guanine nucleotide was determined to 2.85 Angstrom. This GTPase ha s five domains with overall dimensions of 50 x 60 x 118 Angstrom. The GTP binding domain has a core common to other GTPases with a unique su bdomain which probably functions as an intrinsic nucleotide exchange f actor. Domains I and II are homologous to elongation factor Tu and the ir arrangement, both with and without GDP, is more similar to elongati on factor Tu in complex with a GTP analogue than with GDP. Domains III and V show structural similarities to ribosomal proteins. Domain IV p rotrudes from the main body of the protein and has an extraordinary to pology with a left-handed crossover connection between two parallel be ta-strands.