Ka. Martemyanov et al., Mutations in the G-domain of elongation factor G from Thermus thermophilusaffect both its interaction with GTP and fusidic acid, J BIOL CHEM, 276(31), 2001, pp. 28774-28778
Two hypersensitive and two resistant variants of elongation factor-G (EF-G)
toward fusidic acid are studied in comparison with the wild type factor. A
ll mutated proteins are active in a cell-free translation system and riboso
me-dependent GTP hydrolysis. The EF-G variants with the Thr-84 --> Ala or A
sp-109 --> Lys mutations bring about a strong resistance of EF-G to the ant
ibiotic, whereas the EF-Gs with substitutions Gly-16 --> Val or Glu-119 -->
Lys are the first examples of fusidic acid-hypersensitive factors. A corre
lation between fusidic acid resistance of EF-G mutants and their affinity t
o GTP are revealed in this study, although their interactions with GDP are
not changed. Thus, fusidic acid-hypersensitive mutants have the high affini
ty to an uncleavable analog, but the association of resistant mutants with
GTP is decreased. The effects of either fusidic acid-sensitive or resistant
mutations can be explained by the conformational changes in the EF-G molec
ule, which influence its GTP-binding center. The results presented in this
paper indicate that fusidic acid-sensitive mutant factors have a conformati
on favorable for GTP binding and subsequent interaction with the ribosomes.