EF-Tu from E. coli, one of the superfamily of GTPase switch proteins, plays a central role in the fast and accurate delivery of aminoacyl-tRNAs to the translating ribosome. An overview is given about the regulatory effects of methylation, phosphorylation and phage-induced cleavage of EF-Tu on its function. During exponential growth, EF-Tu becomes monomethylated at Lys56 which is converted to Me2Lys upon entering the stationary phase. Lys56 is in the GTPase switch-1 region (residues 49-62), a strongly conserved site involved in interactions with the nucleotide and the 5' end of tRNA. Methylation was found to attenuate GTP hydrolysis and may thus enhance translational accuracy. In vivo 5-10% of EF-Tu is phosphorylated at Thr382 by a ribosome-associated kinase. In EF-Tu-GTP, Thr382 in domain 3 has a strategic position in the interface with domain 1; it is hydrogen-bonded to Glu117 that takes part in the switch-2 mechanism, and is close to the T-stem binding site of the tRNA, in a region known for many kirromycin-resistance mutations. Phosphorylation is enhanced by EF-Ts, but inhibited by kirromycin. In reverse, phosphorylated EF-Tu has an increased affinity for EF-Ts, does not bind kirromycin and can no longer bind aminoacyi tRNA. The in vivo role of this reversible modification is still a matter of speculation. T4 infection of E. coli may trigger a phase-exclusion mechanism by activation of Lit, a host-encoded proteinase. As a result, EF-Tu is cleaved site-specifically between Gly59-Ile60 in the switch-1 region. Translation was found to drop beyond a minimum level. Interestingly, the identical sequence in the related EF-G appeared to remain fully intact. Although the Lit cleavage-mechanism may eventually lead to programmed cell death, the very efficient prevention of phage multiplication may be caused by a novel mechanism of in cis inhibition of late T4 mRNA translation.

Department of Biochemistry Leiden University Netherlands

Zobrazit více v PubMed

EMBO J. 1994 Oct 17;13(20):4877-85 PubMed

Eur J Biochem. 1990 Jul 20;191(1):1-17 PubMed

J Biol Chem. 1998 May 8;273(19):11478-82 PubMed

Biochem Cell Biol. 1995 Nov-Dec;73(11-12):1167-77 PubMed

Biochem Biophys Res Commun. 1997 Sep 18;238(2):370-6 PubMed

Structure. 1993 Sep 15;1(1):35-50 PubMed

J Bacteriol. 1991 May;173(10):3096-100 PubMed

Mol Microbiol. 1994 Mar;11(6):1045-57 PubMed

Structure. 1996 Oct 15;4(10):1153-9 PubMed

Proc Natl Acad Sci U S A. 1977 Aug;74(8):3264-7 PubMed

EMBO J. 1996 Dec 2;15(23):6766-74 PubMed

Eur J Biochem. 1995 Dec 1;234(2):550-6 PubMed

J Biol Chem. 1997 Dec 19;272(51):32206-10 PubMed

Nature. 1991 Jan 10;349(6305):117-27 PubMed

FEBS Lett. 1982 Mar 22;139(2):325-30 PubMed

Prog Nucleic Acid Res Mol Biol. 1983;30:91-126 PubMed

Eur J Biochem. 1986 Nov 3;160(3):557-61 PubMed

Annu Rev Microbiol. 1985;39:557-77 PubMed

J Biol Chem. 1993 Jan 5;268(1):601-7 PubMed

J Biol Chem. 1997 Nov 7;272(45):28252-7 PubMed

Eur J Biochem. 1998 Jan 15;251(1-2):201-7 PubMed

J Biol Chem. 1989 Dec 5;264(34):20518-25 PubMed

J Biol Chem. 1995 Jun 16;270(24):14541-7 PubMed

Proc Natl Acad Sci U S A. 1994 Jan 18;91(2):802-6 PubMed

Structure. 1996 Oct 15;4(10):1141-51 PubMed

Biochimie. 1996;78(11-12):921-33 PubMed

Nature. 1996 Feb 8;379(6565):511-8 PubMed

Eur J Biochem. 1996 Jul 15;239(2):265-71 PubMed

Proc Natl Acad Sci U S A. 1998 Mar 17;95(6):2891-5 PubMed

Nature. 1993 Sep 9;365(6442):126-32 PubMed

Structure. 1996 Mar 15;4(3):229-38 PubMed

FEBS Lett. 1983 Nov 28;164(1):1-8 PubMed

Trends Biochem Sci. 1998 Mar;23 (3):89-91 PubMed

Eur J Biochem. 1980 Jul;108(2):423-31 PubMed

Science. 1995 Dec 1;270(5241):1464-72 PubMed

Proc Natl Acad Sci U S A. 1980 Mar;77(3):1326-30 PubMed

Comparative study of the life cycle dependent post-translation modifications of protein synthesis elongation factor Tu present in the membrane proteome of streptomycetes and mycobacteria