microbiology, Vol 140, 1737-1744, Copyright © 1994 by Society for General Microbiology

ARTICLES

Altered amino acid metabolism in lrp mutants of Escherichia coli K12 and their derivatives

G Ambartsoumian, R D'Ari, RT Lin and EB Newman
Biology Department, Concordia University, Montreal, Quebec, Canada.

An Escherichia coli lrp mutant, lacking the leucine-responsive regulatory protein and the global response it controls, is deregulated in the expression of many genes, but is nevertheless able to grow in glucose-minimal medium at 37 degrees C. In the presence of isoleucine and valine, the growth rate of the lrp mutant at 37 degrees C is significantly increased by exogenous L-serine or L-leucine (or both), suggesting that synthesis of these amino acids is limiting. In the absence of isoleucine and valine, however, growth is severely inhibited by both L-serine and L-leucine. A shift to 42 degrees C or to anaerobiosis makes the lrp mutant auxotrophic for L-serine. Three double mutants carrying lrp and another known mutation, acquire new auxotrophies: lrp relA, lacking the stringent response to amino acid limitation, requires leucine; lrp ssd with numerous metabolic perturbations and antibiotic resistances, requires serine and leucine; and lrp pnt, lacking pyridine nucleotide transhydrogenase, requires glutamate or aspartate (or the corresponding amides). The lrp mutant, although able to achieve balanced growth in some conditions, is clearly on the edge of a metabolic precipice, unable to tolerate many physiological and genetic perturbations which are inocuous to wild-type E. coli.

This article has been cited by other articles:

				U. M. Obiozo, T. H. C. Brondijk, A. J. White, G. van Boxel, T. R. Dafforn, S. A. White, and J. B. Jackson Substitution of Tyrosine 146 in the dI Component of Proton-translocating Transhydrogenase Leads to Reversible Dissociation of the Active Dimer into Inactive Monomers J. Biol. Chem., December 14, 2007; 282(50): 36434 - 36443. [Abstract] [Full Text] [PDF]

				T. H. C. Brondijk, G. I. van Boxel, O. C. Mather, P. G. Quirk, S. A. White, and J. B. Jackson The Role of Invariant Amino Acid Residues at the Hydride Transfer Site of Proton-translocating Transhydrogenase J. Biol. Chem., May 12, 2006; 281(19): 13345 - 13354. [Abstract] [Full Text] [PDF]

				A. K. Mukhopadhyay, J.-Y. Jeong, D. Dailidiene, P. S. Hoffman, and D. E. Berg The fdxA Ferredoxin Gene Can Down-Regulate frxA Nitroreductase Gene Expression and Is Essential in Many Strains of Helicobacter pylori J. Bacteriol., May 1, 2003; 185(9): 2927 - 2935. [Abstract] [Full Text] [PDF]

				S.-p. Hung, P. Baldi, and G. W. Hatfield Global Gene Expression Profiling in Escherichia coli K12. THE EFFECTS OF LEUCINE-RESPONSIVE REGULATORY PROTEIN J. Biol. Chem., October 18, 2002; 277(43): 40309 - 40323. [Abstract] [Full Text] [PDF]

				E. R. Zinser and R. Kolter Prolonged Stationary-Phase Incubation Selects for lrp Mutations in Escherichia coli K-12 J. Bacteriol., August 1, 2000; 182(15): 4361 - 4365. [Abstract] [Full Text]

				J. R. Landgraf, J. A. Boxer, and J. M. Calvo Escherichia coli Lrp (Leucine-Responsive Regulatory Protein) Does Not Directly Regulate Expression of the leu Operon Promoter J. Bacteriol., October 15, 1999; 181(20): 6547 - 6551. [Abstract] [Full Text]

				B. K. Janes and R. A. Bender Two Roles for the Leucine-Responsive Regulatory Protein in Expression of the Alanine Catabolic Operon (dadAB) in Klebsiella aerogenes J. Bacteriol., February 1, 1999; 181(3): 1054 - 1058. [Abstract] [Full Text]

				C. Chen and E. B. Newman Comparison of the Sensitivities of Two Escherichia coli Genes to In Vivo Variation of Lrp Concentration J. Bacteriol., February 1, 1998; 180(3): 655 - 659. [Abstract] [Full Text]