Archaeal elongation factor 1a from Sulfolobus solfataricus interacts with the eubacterial antibiotic GE2270A

The thiazolyl-peptide antibiotic GE2270A, an inhibitor of the elongation factor Tu from Escherichia coli (EcEF-Tu), was used to study the effects produced in the biochemical properties of the archaeal functional analogue elongation factor 1a from Sulfolobus solfa- taricus (SsEF-1a). GE2270A did not substantially affect the poly(U)-directed-poly(Phe) incorporation catalyzed by SsEF-1a and the formation of the ternary complex SsEF-1aÆGTPÆPhe-tRNAPhe. On the other hand, the antibiotic was able to increase the GDP/GTP exchange rate of SsEF-1a; nevertheless, this improvement was not associated with an increase in the catalytic activity of the enzyme. In fact, GE2270A inhibited both the intrinsic GTPase of SsEF-1a (GTPaseNa) and that stimulated by ribosomes. Interestingly, GTPaseNa of both intact and C-terminal-deleted SsEF-1a resulted in a greater sensi- tivity to the antibiotic with respect to SsEF-1a lacking both the M- and C-terminal domains. This result sug- gested that, similar to what is found for EcEF-Tu, the M domain of SsEF-1a is the region of the enzyme most responsible for the interaction with GE2270A. The dif- ferent behavior observed in the inhibition of protein synthesis with respect to EcEF-Tu can be ascribed to the different adaptive structural changes that have occurred in SsEF-1a during evolution.