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Gene Review

trpA  -  tryptophan synthase subunit alpha

Escherichia coli O157:H7 str. Sakai

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Disease relevance of trpA


High impact information on trpA


Biological context of trpA

  • A random single base pair saturation mutagenesis procedure (Myers, R.M., Lerman, L.S., and Maniatis, T. (1985) Science 229, 242-247) was applied in vitro to subcloned fragments of the trpA gene, which codes for this polypeptide [5].
  • Each type of revertant trpA was cloned and its DNA sequence determined. trpA(UGA211) gave rise to two previously unidentified types of missense revertant [6].
  • The mutagenized fragments were subcloned into the plasmid vector and used to transform to ampicillin resistance (Ampr) a recipient strain containing a UGA mutation in trpA [7].
  • These studies also revealed an unpredicted flexibility in the primary amino acid sequence of the trpA product, the alpha subunit of tryptophan synthase [8].
  • The molecular characterization of the mutation that corrected the Eut- phenotype caused by allele Delta903 showed that the new mutation was a deletion of two nucleotides at the tonB-trpA fusion site [9].

Associations of trpA with chemical compounds

  • These trpA fragments were mutagenized in vitro (using nitrous acid, formic acid, hydrazine, and potassium permanganate), and several thousands of mutants have been isolated [5].
  • By analyzing reversion patterns of defined trpA alleles, we showed that pKM101 caused all types of spontaneous base-pair substitution mutations with the possible exception of guanine . cytosine leads to adenine. thymine transitions [10].
  • Low cysteine content (one in trpB; zero in trpA) is a striking feature of these proteins, which may contribute to their thermostability [11].
  • The frequency of reversions induced by one mutagen, methyl methanesulphonate (MMS), increased in proportion to the average number of trpA gene copies per cell, whereas the frequency of reversions induced by the other compounds was dependent on the average number of chromosome replicating forks per cell [12].


  1. Mutant 16S ribosomal RNA: a codon-specific translational suppressor. Murgola, E.J., Hijazi, K.A., Göringer, H.U., Dahlberg, A.E. Proc. Natl. Acad. Sci. U.S.A. (1988) [Pubmed]
  2. Tryptophan operon read-through. Isolation and characterization of an abnormally long tryptophan synthetase alpha subunit from a frame-shift mutant of Escherichia coli. Hardman, J.D., Berger, H., Goodman, M. J. Biol. Chem. (1975) [Pubmed]
  3. Escherichia coli mutant trpA34 has an Asp----Asn change at active site residue 60 of the tryptophan synthetase alpha chain. Shirvanee, L., Horn, V., Yanofsky, C. J. Biol. Chem. (1990) [Pubmed]
  4. Fusion of trpB and trpA of Escherichia coli yields a partially active tryptophan synthetase polypeptide. Yanofsky, C., Paluh, J.L., van Cleemput, M., Horn, V. J. Biol. Chem. (1987) [Pubmed]
  5. In vitro mutagenesis and overexpression of the Escherichia coli trpA gene and the partial characterization of the resultant tryptophan synthase mutant alpha-subunits. Milton, D.L., Napier, M.L., Myers, R.M., Hardman, J.K. J. Biol. Chem. (1986) [Pubmed]
  6. Reversion of trpA nonsense mutations by deletion of the chain-termination codons. Tucker, S.D., Murgola, E.J., Hijazi, K.A. Biochimie (1989) [Pubmed]
  7. Mutations at three sites in the Escherichia coli 23S ribosomal RNA binding region for protein L11 cause UGA-specific suppression and conditional lethality. Murgola, E.J., Xu, W., Arkov, A.L. Nucleic Acids Symp. Ser. (1995) [Pubmed]
  8. A molecular characterization of spontaneous frameshift mutagenesis within the trpA gene of Escherichia coli. Hardin, A., Villalta, C.F., Doan, M., Jabri, M., Chockalingham, V., White, S.J., Fowler, R.G. DNA Repair (Amst.) (2007) [Pubmed]
  9. Molecular characterization of eutF mutants of Salmonella typhimurium LT2 identifies eutF lesions as partial-loss-of-function tonB alleles. Thomas, M.G., O'Toole, G.A., Escalante-Semerena, J.C. J. Bacteriol. (1999) [Pubmed]
  10. Spontaneous mutational specificity of drug resistance plasmid pKM101 in Escherichia coli. Fowler, R.G., McGinty, L., Mortelmans, K.E. J. Bacteriol. (1979) [Pubmed]
  11. Cloning and sequence analysis of tryptophan synthetase genes of an extreme thermophile, Thermus thermophilus HB27: plasmid transfer from replica-plated Escherichia coli recombinant colonies to competent T. thermophilus cells. Koyama, Y., Furukawa, K. J. Bacteriol. (1990) [Pubmed]
  12. Physiological modification of alkylating agent induced mutagenesis. II. Influence of the numbers of chromosome replicating forks and gene copies on the frequency of mutations induced in Escherichia coli. Hince, T.A., Neale, S. Mutat. Res. (1977) [Pubmed]
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