PMID:9560382
| Citation |
Timms, AR and Bridges, BA (1998) Reversion of the tyrosine ochre strain Escherichia coli WU3610 under starvation conditions depends on a new gene tas. Genetics 148:1627-35 |
|---|---|
| Abstract |
When 3 x 10(8) bacteria of the Escherichia coli tyrA14(oc) leu308(am) strain WU3610 are plated on glucose salts agar supplemented with leucine only, colonies of slow-growing Tyr+ suppressor mutants begin to appear after about a week and increase in numbers roughly linearly with time thereafter (stationary phase or starvation-associated mutation). From a library constructed from two of these mutants, a clone was obtained that suppressed the tyrosine requirement of WU3610 when present on a multicopy plasmid. The activity was identified to an open reading frame we call tas, the sequence for which has homology with a variety of known genes with aldo-keto reductase activity. The activity of tas complements the prephenate dehydrogenase dysfunction of tyrA14 (the chorismate mutase activity of tyrA possibly being still functional). A strain deleted for tas showed no spontaneous mutation under starvation conditions. Whereas neither tas+ nor tas bacteria showed any increase in viable or total count when plated under conditions of tyrosine starvation at 3 x 10(8) cells per plate, at lower density (approximately 10(7) per plate) tas+ but not tas bacteria showed considerable residual growth. We suggest that the single copy of tas present in WU3610 allows cryptic cell or DNA turnover under conditions of tyrosine starvation and that this is an essential prerequisite for starvation-associated mutation in this system. The target gene for mutation is not tas, although an increase in the expression of this gene, for example, resulting from a suppressor mutation affecting supercoiling, could be responsible for the slow-growing Tyr+ phenotype. |
| Links | |
| Keywords |
Alcohol Oxidoreductases/genetics; Animals; Base Sequence; Cloning, Molecular; Culture Media; DNA, Bacterial; Escherichia coli/genetics; Escherichia coli/growth & development; Escherichia coli/metabolism; Gene Deletion; Genes, Bacterial; Genetic Complementation Test; Humans; Molecular Sequence Data; Prephenate Dehydrogenase/genetics; Tyrosine/metabolism |
| edit table |
Significance
You can help EcoliWiki by summarizing why this paper is useful
Useful Materials and Methods
You can help Ecoliwiki by describing the useful materials (strains, plasmids, antibodies, etc) described in this paper.
Annotations
<protect><annotationlinks/></protect>
EcoliWiki Links
Add links to pages that link here (e.g. gene, product, method pages)
See also
References
See Help:References for how to manage references in EcoliWiki.
