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Gene Review

trpA  -  tryptophan synthase, alpha subunit

Escherichia coli str. K-12 substr. MG1655

Synonyms: ECK1254, JW1252, try, tryp
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Disease relevance of trpA

  • Nucleotide sequences of trpA of Salmonella typhimurium and Escherichia coli: an evolutionary comparison [1].
  • After our first observation of codon context effects in missense suppression ( Murgola & Pagel , 1983), we measured the suppression of missense mutations at two positions in trpA in Escherichia coli [2].
  • Codon usage in these Pseudomonas genes shows a marked preference for codons ending in G or C, thereby resembling that of trpB, trpA, and several other chromosomal loci from this species and others with a high G + C content in their DNA [3].
  • The suppressor allows readthrough of UGA mutations at two positions in trpA and at two sites in bacteriophage T4 [4].
  • To reveal the properties and potential physiological role of TrpB2, the trpA, trpB1, and trpB2 genes of Thermotoga maritima were expressed heterologously in Escherichia coli, and the resulting proteins were purified and characterized [5].

High impact information on trpA

  • In this study it is shown that, under conditions of intense selection, a strain carrying missense mutations in both trpA and trpB reverts to Trp+ 10(8) times more frequently than would be expected if the two mutations were the result of independent events [6].
  • The suppressor also does not allow mistranslation of the UGA-related trpA missense mutations UGG at positions 211 and 234, AGA at 211 and 234, CGA at 211, or UGU and UGC at 234 [4].
  • The TrpA and TrpB1 proteins are encoded by the adjacent trpA and trpB1 genes in the trp operon [5].
  • The mutant alpha subunits, obtained by in vitro random, saturation mutagenesis of the encoding trpA gene, contain single amino acid substitutions at sites within the first 121 residues of the alpha polypeptide [7].
  • Analysis of trpA expression in these deletion mutants established that the ribosome binding site sequence is required for efficient translation of the trpA segment of trp mRNA [8].

Chemical compound and disease context of trpA


Biological context of trpA


Anatomical context of trpA


Associations of trpA with chemical compounds

  • The mRNA sites of the codons correspond to amino acids 211 and 234 of the trpA polypeptide, positions at which glycine is the wild-type amino acid [2].
  • The suppressible codons in the trpA messenger RNA were the lysine codons, AAA and AAG, and the glutamic acid codons, GAA and GAG [2].
  • We also observed that excess N was able to suppress transcriptional polarity in the particular case of cloned 'trpA, the last gene of the tryptophan operon, although there was no effect on polarity within chromosomal trpE [19].
  • The majority of the enzymatically defective mutant alpha subunits have decreased capacities for substrate (indole-3-glycerol phosphate) utilization, typical of the early trpA missense mutants isolated by in vivo selection methods [20].
  • 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 [21].

Physical interactions of trpA

  • To examine the dependence of trpA expression on the ribosome binding site sequence in the distal segment of trpB, deletions were produced that replaced this trpB sequence [8].

Other interactions of trpA

  • Translation of trpB is terminated by single UGA codon, which overlaps the trpA AUG initiation codon: UGAUG [14].
  • A trp-lac fusion system was used in which part of the trpA gene is fused to the lacZ gene [10].
  • C-terminal deletions or fusions of the livK gene to trpA (encoding the alpha subunit of tryptophan synthetase) were secreted with little loss of efficiency [1] [22].

Analytical, diagnostic and therapeutic context of trpA


  1. Nucleotide sequences of trpA of Salmonella typhimurium and Escherichia coli: an evolutionary comparison. Nichols, B.P., Yanofsky, C. Proc. Natl. Acad. Sci. U.S.A. (1979) [Pubmed]
  2. Codon context effects in missense suppression. Murgola, E.J., Pagel, F.T., Hijazi, K.A. J. Mol. Biol. (1984) [Pubmed]
  3. Structure and regulation of the anthranilate synthase genes in Pseudomonas aeruginosa: I. Sequence of trpG encoding the glutamine amidotransferase subunit. Crawford, I.P., Eberly, L. Mol. Biol. Evol. (1986) [Pubmed]
  4. 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]
  5. A novel tryptophan synthase beta-subunit from the hyperthermophile Thermotoga maritima. Quaternary structure, steady-state kinetics, and putative physiological role. Hettwer, S., Sterner, R. J. Biol. Chem. (2002) [Pubmed]
  6. Adaptive evolution that requires multiple spontaneous mutations: mutations involving base substitutions. Hall, B.G. Proc. Natl. Acad. Sci. U.S.A. (1991) [Pubmed]
  7. Enzymatic properties of mutant Escherichia coli tryptophan synthase alpha-subunits. Lim, W.K., Sarkar, S.K., Hardman, J.K. J. Biol. Chem. (1991) [Pubmed]
  8. A ribosome binding site sequence is necessary for efficient expression of the distal gene of a translationally-coupled gene pair. Das, A., Yanofsky, C. Nucleic Acids Res. (1984) [Pubmed]
  9. Structure and function of the trp operon control regions of Brevibacterium lactofermentum, a glutamic-acid-producing bacterium. Sano, K., Matsui, K. Gene (1987) [Pubmed]
  10. Translational coupling of the trpB and trpA genes in the Escherichia coli tryptophan operon. Aksoy, S., Squires, C.L., Squires, C. J. Bacteriol. (1984) [Pubmed]
  11. Suppressors of lysine codons may be misacylated lysine tRNAs. Murgola, E.J., Pagel, F.T. J. Bacteriol. (1983) [Pubmed]
  12. Ordering tryptophan synthase genes of Pseudomonas aeruginosa by cloning in Escherichia coli. Manch, J.N., Crawford, I.P. J. Bacteriol. (1981) [Pubmed]
  13. Induction of specific base-pair substitutions in E. coli trpA mutants by chloroethylene oxide, a carcinogenic vinyl chloride metabolite. Barbin, A., Besson, F., Perrard, M.H., Béréziat, J.C., Kaldor, J., Michel, G., Bartsch, H. Mutat. Res. (1985) [Pubmed]
  14. An intercistronic region and ribosome-binding site in bacterial messenger RNA. Platt, T., Yanofsky, C. Proc. Natl. Acad. Sci. U.S.A. (1975) [Pubmed]
  15. Missense and nonsense suppressors can correct frameshift mutations. Tucker, S.D., Murgola, E.J., Pagel, F.T. Biochimie (1989) [Pubmed]
  16. Restoration of a translational stop-start overlap reinstates translational coupling in a mutant trpB'-trpA gene pair of the Escherichia coli tryptophan operon. Das, A., Yanofsky, C. Nucleic Acids Res. (1989) [Pubmed]
  17. Comparison of the nucleoside sequence of trpA and sequences immediately beyond the trp operon of Klebsiella aerogenes. Salmonella typhimurium and Escherichia coli. Nichols, B.P., Blumenberg, M., Yanofsky, C. Nucleic Acids Res. (1981) [Pubmed]
  18. Solubilization and renaturation of overexpressed aggregates of mutant tryptophan synthase alpha-subunits. Lim, W.K., Smith-Somerville, H.E., Hardman, J.K. Appl. Environ. Microbiol. (1989) [Pubmed]
  19. Overexpression of N antitermination proteins of bacteriophages lambda, 21, and P22: loss of N protein specificity. Franklin, N.C., Doelling, J.H. J. Bacteriol. (1989) [Pubmed]
  20. Relative activities and stabilities of mutant Escherichia coli tryptophan synthase alpha subunits. Lim, W.K., Shin, H.J., Milton, D.L., Hardman, J.K. J. Bacteriol. (1991) [Pubmed]
  21. 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]
  22. Secretion of mutant leucine-specific binding proteins with internal deletions in Escherichia coli. Adams, M.D., Oxender, D.L. J. Cell. Biochem. (1991) [Pubmed]
  23. Arabidopsis thaliana tryptophan synthase alpha: gene cloning, expression, and subunit interaction. Radwanski, E.R., Zhao, J., Last, R.L. Mol. Gen. Genet. (1995) [Pubmed]
  24. Third position base changes in codons 5' and 3' adjacent UGA codons affect UGA suppression in vivo. Buckingham, R.H., Sörensen, P., Pagel, F.T., Hijazi, K.A., Mims, B.H., Brechemier-Baey, D., Murgola, E.J. Biochim. Biophys. Acta (1990) [Pubmed]
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