Elongation factor Tu3 (EF-Tu3) from the kirromycin producer Streptomyces ramocissimus Is resistant to three classes of EF-Tu-specific inhibitors.

The antibiotic kirromycin inhibits prokaryotic protein synthesis by immobilizing elongation factor Tu (EF-Tu) on the elongating ribosome. Streptomyces ramocissimus, the producer of kirromycin, contains three tuf genes. While tuf1 and tuf2 encode kirromycin-sensitive EF-Tu species, the function of tuf3 is unknown.

The unique tuf2 gene from the kirromycin producer Streptomyces ramocissimus encodes a minor and kirromycin-sensitive elongation factor Tu.

Streptomyces ramocissimus, the producer of elongation factor Tu (EF-Tu)-targeted antibiotic kirromycin, contains three divergent tuf-like genes, with tuf1 encoding regular kirromycin-sensitive EF-Tu1; the functions of tuf2 and tuf3 are unknown. Analysis of the tuf gene organization in nine producers of kirromycin-type antibiotics revealed that they all contain homologues of tuf1 and sometimes of tuf3 but that tuf2 was found in S. ramocissimus only.