Mutants of Escherichia coli altered in both genes coding for the elongation factor Tu.

Abstract

Genetic analysis of a mutant of Escherichia coli resistant to the antibiotic mocimycin is presented. This resistance is due to alterations in both tuf genes coding for the elongation factor Tu. Mocimycin resistance is recessive. Bacteria carryong only one tuf gene from the resistant mutant are still mocimycin sensitive. If the mutant gene is the tufA gene, the seisitive cells can be made resistant through inactivation of the tufB gene by insertion of the bacteriophage milliunits genome. Conditional mocimycin-resistant mutants ban also be isolated when the tufB gene is altered by an amber or a temperature-sensitive mutation. When only the tufB allele from the original mocimycin-resistant mutant is present, inactivation of the wild-type tufA gene fails to give viable mocimycin-resistant progeny. We conclude that the tufA mutant allele codes for a functional mocimycin-resistant EF-Tu, whereas the mutant tufB gene does not code for a functional product.

Allosteric changes of the guanine nucleotide site of elongation factor EF‐Tu

“…a Originally the EF-Tu produced by D2216 was designated to be a tufB product by genetic evidence [8]. In [16] however, it appeared to be a tufA product from endgroup determination b tufB of LBE2045 was inactivated by insertion of bacteriophage Mu [5,20] 'A' and 'B' refer to tufA and tufB, respectively, the genes encoding EF-Tu; subscripts, S, sensitive; R resistant Each assay (75 ul) contained 50 mM imidazole acetate (pH 7.5), 50 mM KC1, 10 mM MgC12, 0.4 mM GTP, 0.3 mM ATP, 2.6 mM phosphoenylpyruvate, 1 tag pyruvate kinase, 4 vg poly(U), 40 pmol ribosomes, 120 pmol [14C]Phe (900 cpm/pmol), 7 pmol elongation factor G, 88/~g tRNAtntal, 10 pmol elongation factor EF-Ts, 10 pmol EF-Tu and tRNAPhe-synthetase.…”

“…During the elongation cycle of protein biosynthesis it plays an essential role in the correct placement of aminoacyl-tRNA onto the ribosome-messenger RNA complex [1,2]. In Escherichia coli two genes, tufA and tufB, code for EF-Tu [3][4][5]. The primary structure of the polypeptide chain of these two gene products is identical, only the C-terminal residue is different [6].…”

“…We have isolated mutant E. coli strains resistant to the antibiotic kirromycin [5,8]. This antibiotic inhibits the elongation cycle of protein biosynthesis by preventing the release of EF-Tu from the ribosome after hydrolysis of GTP, thus blocking the ribosome on the messenger RNA [9][10][11].…”

Kirromycin‐resistant elongation factor Tu from wild‐type of Lactobacillus brevis

“…Mutants of Escherichia coli and Bacillus subtilis selected for resistance to kirromycin have been shown to possess an altered form of EF-Tu [3][4][5]. Acquisition of kirromycin resistance introduces functionally related modifications of the EF-Tu nucleotide-binding site [3,4].…”

A kirromycin resistant elongation factor EF‐Tu from Escherichia coli contains a threonine instead of an alanine residue in position 375

“…Two unlinked genes coding for EF-Tu have been identified on the E. coli chromosome [8][9][10]. One designated tufA maps at 72 rain, the other, designated tufB, at 88 min.…”