Structure of a mutant EF-G reveals domain III and possibly the fusidic acid binding site

The crystal structure of Thermus thermophilus elongation factor G (EF-G) carrying the point mutation His573Ala was determined at a resolution of 2.8 Angstrom. The mutant has a more closed structure than that previously reported for wild-type EF-G. This is obtained by a 10 degrees rigid rotation of domains III, TV and V with regard to domains I and II. This rotation results in a displacement of the tip of domain TV by approximately 9 Angstrom. The structure of domain III is now fully visible and reveals the double split beta-alpha-beta motif also observed for EFG domain V and for several ribosomal proteins. A large number of fusidic acid resistant mutations found in domain III have now been possible to locate. Possible locations for the effector loop and a possible binding site for fusidic acid are discussed in relation to some of the fusidic acid resistant mutations. (C) 2000 Academic Press.