Conformational alteration of protein synthesis elongation factor EF-Tu by EF-Ts and by kirromycin.

Abstract

Alterations of the structure of EF[elongation factor]-Tu were investigated by using the rate of EF-Tu cleavage by trypsin as a conformational probe. The presence of EF-Ts bound to EF-Tu resulted in a 10-fold increase in the cleavage rate. The antibiotic kirromycin, which inhibited protein synthesis by its interaction with EF-Tu, mimicked this effect of EF-Ts. Kirromycin and EF-Ts also facilitated the exchange of free GDP with GDP bound to EF-Tu. EF-Ts and kirromycin induced a similar conformational change in EF-Tu, thereby opening the guanine nucleotide binding site. The trypsin-cleaved EF-Tu still could bind GDP and EF-Ts and could function in Q.beta. replicase, but it no longer spontaneously renatured following denaturation in urea.