Disease relevance of thyA

• Finally, by applying the target-site recognition rules, we show that the L1.LtrB intron can be modified to insert at new sites in a plasmid-borne thyA gene in Escherichia coli [1].
• By regulating expression of this gene from the phage lambda pL promoter within pKC30 in a thyA host containing a temperature-sensitive lambda repressor, the T4 synthetase could be amplified about 200-fold over that after T4 infection [2].
• We show here that the mutant prophage Mu gem2ts can excise precisely from at least three separate loci -- malT, lac and thyA (selected as Mal+, Lac+ and Thy+, respectively) [3].
• The kanamycin-resistance gene was also deleted from pK184 and was replaced with Salmonella typhimurium thyA [4].
• Haemocin, a bacteriocin produced by Haemophilus influenzae b, caused pronounced cell elongation of the sensitive strains H. influenzae Rd and Escherichia coli CR34 thyA [5].

High impact information on thyA

• The amino-terminal sequence of thymidylate synthase (5,10-methylenetetrahydrofolate:dUMP C-methyltransferase, EC 2.1.1.45), the product of the thyA gene, located the 792-base-pair open reading frame, which codes for the 264 amino acid residues of this enzyme [6].
• The nucleotide sequence of a 1,163-base-pair fragment that encodes the entire thyA gene of Escherichia coli K-12 was determined [6].
• Production of H(4)folate rather than H(2)folate, as in the classical thymidylate synthase reaction, eliminates the need for dihydrofolate reductase, explaining the trimethoprim-resistant phenotype displayed by thyA(-) E. coli-expressing CTThyX [7].
• In contrast to the extensively characterized thyA-encoded thymidylate synthases, which form a ternary complex with substrates dUMP and CH(2)H(4)folate and follow an ordered sequential mechanism, CTThyX follows a ping-pong kinetic mechanism involving a methyl enzyme intermediate [7].
• Because both wild type and thymidylate synthase-deficient phenotypes are selectable on the appropriate growth medium, these thyA mutants could be used for genetic selections of protease inhibitors and analysis of protease specificities [8].

Chemical compound and disease context of thyA

• A natural mutational hotspot in the thyA gene of Escherichia coli accounts for over half of the mutations that inactivate this gene, which can be selected by resistance to the antibiotic trimethoprim [9].
• In 1954, Cohen and Barner discovered that a thymine auxotrophic (thyA) mutant of Escherichia coli undergoes cell death in response to thymine starvation [10].
• Escherichia coli (thyA DeltafolA) mutants are viable and can grow in minimal medium when supplemented with thymidine alone [11].
• The B. hermsii thyX gene complemented the thyA mutation in E. coli, and purified B. hermsii ThyX protein catalyzed the conversion of dTMP from dUMP [12].
• In transformation experiments with thyA mutants of E. coli and conjugation experiments with thyA mutants of R. meliloti, the lactococcal thyA gene permitted selection of transformants and transconjugants with the same efficiency as did genes for resistance to ampicillin, chloramphenicol, or tetracycline [13].

Biological context of thyA

• We have carried out an extensive insertional mutagenesis of the Escherichia coli TS gene (thyA) using three different methods [8].
• Surprisingly, inversion of the thyA operon on the chromosome did not abolish thyA131 hotspot mutagenesis, indicating that mutagenesis at this site occurs during both leading and lagging-strand synthesis [9].
• We also describe the construction of thyA-based plasmids with the Vibrio cholerae rfb genes (encoding O-antigen biosynthesis of the Inaba serotype) [14].
• The nucleotide sequence of the lactococcal thyA gene was determined by the dideoxy-chain termination technique [15].
• DNA-DNA hybridizations demonstrated that the thyA gene is encoded by the chromosome of L. lactis subsp. lactis [15].

Associations of thyA with chemical compounds

• Similarly, the binding of dUMP by F3-TS was greatly diminished relative to thyA-TS, but its binding as well as that of FdUMP could be improved by the presence of either the folate substrate or a tight binding folate analogue, 10-propargyl-5,8-dideazafolate (PDDF) [16].
• We also deleted the thyA gene from this strain, rendering it thymine dependent [4].
• This plasmid will permit growth of thyA mutant strains in the absence of thymidine or thymine and has a number of unique restriction sites which can be used for cloning [13].
• The selected L. acidophilus DOM La strain carries a mutated thyA gene and has an obligate requirement for thymidine [17].
• Portions of the genomes (including the tnaA and thyA genes, the trp operon, and one other unassigned segment) appear to have evolved in concert with the genome as a whole [18].

Analytical, diagnostic and therapeutic context of thyA

• Molecular cloning of the wild-type and mutant thyA gene from Shigella flexneri Y [19].
• The thyA gene which codes for thymidylate synthase has been cloned and sequenced from the wild-type Shigella flexneri Y strain SH4 and a thyA mutant TSF21 after amplifying the gene by polymerase chain reaction (PCR) [19].
• The localization of SeqA, thymidylate synthase, DnaB (helicase) and the DNA polymerase components alpha and tau, has been studied by immunofluorescence microscopy [20].
• Using kinetic and X-ray crystallography experiments, we have examined the role of the highly conserved Tyr-261 in the catalytic mechanism of TS [21].

References