3ZZ0: Crystal Structure Of Ribosomal Elongation Factor (Ef)-G From Staphylococcus Aureus With A Fusidic Acid Hyper-Sensitivity Mutation M16i

Antibiotic resistance in bacteria is often associated with fitness loss, which is compensated by secondary mutations. Fusidic acid (FA), an antibiotic used against pathogenic bacteria Staphylococcus aureus, locks elongation factor-G (EF-G) to the ribosome after GTP hydrolysis. To clarify the mechanism of fitness loss and compensation in relation to FA resistance, we have characterized three S. aureus EF-G mutants with fast kinetics and crystal structures. Our results show that a significantly slower tRNA translocation and ribosome recycling, plus increased peptidyl-tRNA drop-off, are the causes for fitness defects of the primary FA-resistant mutant F88L. The double mutant F88L/M16I is three to four times faster than F88L in both reactions and showed no tRNA drop-off, explaining its fitness compensatory phenotype. The M16I mutation alone showed hypersensitivity to FA, higher activity, and somewhat increased affinity to GTP. The crystal structures demonstrate that Phe-88 in switch II is a key residue for FA locking and also for triggering interdomain movements in EF-G essential for its function, explaining functional deficiencies in F88L. The mutation M16I loosens the hydrophobic core in the G domain and affects domain I to domain II contact, resulting in improved activity both in the wild-type and F88L background. Thus, FA-resistant EF-G mutations causing fitness loss and compensation operate by affecting the conformational dynamics of EF-G on the ribosome.
PDB ID: 3ZZ0Download
MMDB ID: 101323
PDB Deposition Date: 2011/8/30
Updated in MMDB: 2012/09
Experimental Method:
x-ray diffraction
Resolution: 2.8  Å
Source Organism:
Similar Structures:
Biological Unit for 3ZZ0: monomeric; determined by author and by software (PISA)
Molecular Components in 3ZZ0
Label Count Molecule
Protein (1 molecule)
Elongation Factor G
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB