AN ELONGATION-FACTOR TU (EF-TU) RESISTANT TO THE EF-TU INHIBITOR GE2270 IN THE PRODUCING ORGANISM PLANOBISPORA-ROSEA

Using a cell-free protein-synthesis system, we have established that t he elongation factor (EF) Tu (EF-Tu) of the actinomycete Planobispora roses, the producer of the thiazolyl peptide GE2270, a specific EF-Tu inhibitor, is highly resistant to its own antibiotic, while it is comp letely inhibited by kirromycin, which is another inhibitor of this fac tor, P. rosea was found to possess a single tuf gene, located between fus and rpsJ, encoding other components of the protein-synthesis machi nery. The P. rosea tuf gene was expressed as a translational fusion to malE in Escherichia coli, and the resulting EF-Tu with an N-terminal Gly-Met extension was able to promote poly(U)-directed poly(Phe) synth esis in cell-free systems. This activity was not affected by GE2270, a nd the recombinant protein was incapable of binding the antibiotic, in dicating that the P. roses EF-Tu is intrinsically resistant to this in hibitor. Inspection of the translated tuf sequence revealed a number o f amino acid substitutions in highly conserved positions. These residu es, which are likely to be involved in conferring GE2270 resistance, m ap in EF-Tu domain II, as do the only two known mutations conferring r esistance to this class of thiazolyl peptides in Bacillus subtilis.