7 research outputs found
Studies withSalmonella typhimurium mutants defective in enzymes of the propionate catabolism
Tumor Targeting via Sialic Acid: [68Ga]DOTA-en-pba as a New Tool for Molecular Imaging of Cancer with PET
Metabolic Context and Possible Physiological Themes of Ï‚(54)-Dependent Genes in Escherichia coli
Ï‚(54) has several features that distinguish it from other sigma factors in Escherichia coli: it is not homologous to other Ï‚ subunits, Ï‚(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 Ï‚(54)-dependent genes. Surveys of Ï‚(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 Ï‚(54)-dependent genes from a potentially coherent metabolic context. To address this concern, we consider the function and metabolic context of Ï‚(54)-dependent genes primarily from a single organism, Escherichia coli, in which a reasonably complete list of Ï‚(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 Ï‚(54)-dependent operons, and about half are involved in nitrogen assimilation and metabolism. A possible physiological relationship between Ï‚(54)-dependent genes may be based on the fact that nitrogen assimilation consumes energy and intermediates of central metabolism. The products of the Ï‚(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 Ï‚(54)-dependent genes within a single organism and may partially account for the unique features of Ï‚(54) and Ï‚(54)-dependent gene expression