3ZZT

Mechanism of Elongation Factor-G-Mediated Fusidic Acid Resistance and Fitness Compensation in Staphylococcus Aureus.

(2012) J Biol Chem 287: 30257

• PubMed: 22767604 Search on PubMedSearch on PubMed Central
• DOI: https://doi.org/10.1074/jbc.M112.378521
• Primary Citation of Related Structures:  
  3ZZ0, 3ZZT, 3ZZU


• PubMed Abstract: 
  

  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.

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Organizational Affiliation: 

Department of Cell and Molecular Biology, Uppsala University, 75124 Uppsala, Sweden.