PMID:11528004
| Citation |
Reitzer, L and Schneider, BL (2001) Metabolic context and possible physiological themes of sigma(54)-dependent genes in Escherichia coli. Microbiol. Mol. Biol. Rev. 65:422-44, table of contents |
|---|---|
| Abstract |
Sigma(54) has several features that distinguish it from other sigma factors in Escherichia coli: it is not homologous to other sigma subunits, sigma(54)-dependent expression absolutely requires an activator, and the activator binding sites can be far from the transcription start site. A rationale for these properties has not been readily apparent, in part because of an inability to assign a common physiological function for sigma(54)-dependent genes. Surveys of sigma(54)-dependent genes from a variety of organisms suggest that the products of these genes are often involved in nitrogen assimilation; however, many are not. Such broad surveys inevitably remove the sigma(54)-dependent genes from a potentially coherent metabolic context. To address this concern, we consider the function and metabolic context of sigma(54)-dependent genes primarily from a single organism, Escherichia coli, in which a reasonably complete list of sigma(54)-dependent genes has been identified by computer analysis combined with a DNA microarray analysis of nitrogen limitation-induced genes. E. coli appears to have approximately 30 sigma(54)-dependent operons, and about half are involved in nitrogen assimilation and metabolism. A possible physiological relationship between sigma(54)-dependent genes may be based on the fact that nitrogen assimilation consumes energy and intermediates of central metabolism. The products of the sigma(54)-dependent genes that are not involved in nitrogen metabolism may prevent depletion of metabolites and energy resources in certain environments or partially neutralize adverse conditions. Such a relationship may limit the number of physiological themes of sigma(54)-dependent genes within a single organism and may partially account for the unique features of sigma(54) and sigma(54)-dependent gene expression. |
| Links |
PubMed PMC99035 Online version:10.1128/MMBR.65.3.422-444.2001 |
| Keywords |
DNA-Binding Proteins; DNA-Directed RNA Polymerases/chemistry; DNA-Directed RNA Polymerases/physiology; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli/physiology; Escherichia coli Proteins; Gene Expression; Genes, Bacterial; Nitrogen/metabolism; Promoter Regions, Genetic; RNA Polymerase Sigma 54; Sigma Factor/chemistry; Sigma Factor/physiology; Transcription, Genetic |
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