cysQ, a gene needed for cysteine synthesis in Escherichia coli K-12 only during aerobic growth
Open Access
- 1 January 1992
- journal article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 174 (2), 415-425
- https://doi.org/10.1128/jb.174.2.415-425.1992
Abstract
The initial steps in assimilation of sulfate during cysteine biosynthesis entail sulfate uptake and sulfate activation by formation of adenosine 5'-phosphosulfate, conversion to 3'-phosphoadenosine 5'-phosphosulfate, and reduction to sulfite. Mutations in a previously uncharacterized Escherichia coli gene, cysQ, which resulted in a requirement for sulfite or cysteine, were obtained by in vivo insertion of transposons Tn5tac1 and Tn5supF and by in vitro insertion of resistance gene cassettes. cysQ is at chromosomal position 95.7 min (kb 4517 to 4518) and is transcribed divergently from the adjacent cpdB gene. A Tn5tac1 insertion just inside the 3' end of cysQ, with its isopropyl-beta-D-thiogalactopyranoside-inducible tac promoter pointed toward the cysQ promoter, resulted in auxotrophy only when isopropyl-beta-D-thiogalactopyranoside was present; this conditional phenotype was ascribed to collision between converging RNA polymerases or interaction between complementary antisense and cysQ mRNAs. The auxotrophy caused by cysQ null mutations was leaky in some but not all E. coli strains and could be compensated by mutations in unlinked genes. cysQ mutants were prototrophic during anaerobic growth. Mutations in cysQ did not affect the rate of sulfate uptake or the activities of ATP sulfurylase and its protein activator, which together catalyze adenosine 5'-phosphosulfate synthesis. Some mutations that compensated for cysQ null alleles resulted in sulfate transport defects. cysQ is identical to a gene called amtA, which had been thought to be needed for ammonium transport. Computer analyses, detailed elsewhere, revealed significant amino acid sequence homology between cysQ and suhB of E. coli and the gene for mammalian inositol monophosphatase. Previous work had suggested that 3'-phosphoadenoside 5'-phosphosulfate is toxic if allowed to accumulate, and we propose that CysQ helps control the pool of 3'-phosphoadenoside 5'-phosphosulfate, or its use in sulfite synthesis.Keywords
This publication has 45 references indexed in Scilit:
- Diverse proteins homologous to inositol monophosphataseFEBS Letters, 1991
- Ammonium transport in Escherichia coli: localization and nucleotide sequence of the amtA geneJournal of General Microbiology, 1991
- The physical map of the whole E. coli chromosome: Application of a new strategy for rapid analysis and sorting of a large genomic libraryCell, 1987
- Novel regulatory mutants of the phosphate regulon in Escherichia coli K-12Journal of Molecular Biology, 1986
- Two Separate Genes Involved In Sulphate Transport In Escherichia coli K12Microbiology, 1983
- Construction and characterization of the chloramphenicol-resistance gene cartridge: A new approach to the transcriptional mapping of extrachromosomal elementsGene, 1982
- Isolation of Escherichia coli Mutants (cpdB) Deficient in Periplasmic 2' :3' -Cyclic Phosphodiesterase and Genetic Mapping of the cpdB LocusMicrobiology, 1980
- Analysis of gene control signals by DNA fusion and cloning in Escherichia coliJournal of Molecular Biology, 1980
- Cysteine Auxotrophs of Salmonella typhimurium which Grow without Cysteine in a Hydrogen/Carbon Dioxide AtmosphereJournal of General Microbiology, 1979
- Regulation of the Assimilation of Nitrogen CompoundsAnnual Review of Biochemistry, 1978