Elongation factor Tu: a molecular switch in protein biosynthesis

Summary Elongation factor Tu (EF‐Tu), the most abundant protein in Escherichia coli, is a guanine nucleotide‐binding protein that in the ‘on’ state acts as a carrier of amino acyl‐tRNA to the ribosome. Our knowledge of this essential component of translation has brought substantial progress in the past decade thanks to the co‐ordinated application of biochemical, physico‐chemical and genetic methods. Crystallographic analysis at 2.6 Å resolution and site‐directed mutagenesis have revealed structural and functional similarities between the guanine nucleotide‐binding domains of EF‐Tu and human H‐ras p21 protein. The regulation of the expression of the two EF‐Tu‐encoding genes in E. coli, particularly that of tufB, has been shown to involve diverse mechanisms. Several aspects of the functions of EF‐Tu in the elongation cycle have been reinvestigated, leading to new insights. These studies have emphasized the manifold aspects of the mechanisms regulating the activity of EF‐Tu in the bacterial cell.