Fusidic acid (FA) is a steroid antibiotic commonly used against Gram positive bacterial infections. It inhibits protein synthesis by stalling elongation factor G (EF-G) on the ribosome after translocation. A significant number of the mutations confer ...
Fusidic acid (FA) is a steroid antibiotic commonly used against Gram positive bacterial infections. It inhibits protein synthesis by stalling elongation factor G (EF-G) on the ribosome after translocation. A significant number of the mutations conferring strong FA resistance have been mapped at the interfaces between domains G, III and V of EF-G. However, direct information on how such mutations affect the structure has hitherto not been available. Here we present the crystal structures of two mutants of Thermus thermophilus EF-G, G16V and T84A, which exhibit FA hypersensitivity and resistance in vitro, respectively. These mutants also have higher and lower affinity for GTP respectively than wild-type EF-G. The mutations cause significant conformational changes in the switch II loop that have opposite effects on the position of a key residue, Phe90, which undergoes large conformational changes. This correlates with the importance of Phe90 in FA sensitivity reported in previous studies. These structures substantiate the importance of the domain G/domain III/domain V interfaces as a key component of the FA binding site. The mutations also cause subtle changes in the environment of the "P-loop lysine", Lys25. This led us to examine the conformation of the equivalent residue in all structures of translational GTPases, which revealed that EF-G and eEF2 form a group separate from the others and suggested that the role of Lys25 may be different in the two groups.
Related Citations:
Structure of a Mutant EF-G Reveals Domain III and Possibly the Fusidic Acid Binding Site Laurberg, M.,Kristensen, O.,Martemyanov, K.,Gudkov, A.T.,Nagaev, I.,Hughes, D.,Liljas, A. (2000) J.Mol.Biol. 303: 593
Mutations in the G-Domain of Elongation Factor G from Thermus Thermophilus Affect Both its Interaction with GTP and Fusidic Acid. Martemyanov, K.A.,Liljas, A.,Yarunin, A.S.,Gudkov, A.T. (2001) J.Biol.Chem. 276: 28774
The Crystal Structure of Elongation Factor G Complexed with Gdp, at 2.7 A Resolution Czworkowski, J.,Wang, J.,Steitz, T.A.,Moore, P.B. (1994) Embo J. 13: 3661
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The Structure of Elongation Factor G in Complex with Gdp: Conformational Flexibility and Nucleotide Exchange Al-Karadaghi, S.,Aevarsson, A.,Garber, M.,Zheltonosova, J.,Liljas, A. (1996) Structure 4: 555
Organizational Affiliation:
Department of Molecular Biophysics, Lund University, Box 124, S-221 00 Lund, Sweden.
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