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Copyright of Reanimation is the property of Lavoisier and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Reanimation is the property of Lavoisier and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Availability of O is one of the most important regulatory signals in facultatively anaerobic bacteria. Various two- or one-component sensor/regulator systems control the expression of aerobic and anaerobic metabolism in response to O. Most of the sensor proteins contain heme or Fe as cofactors that interact with O either by binding or by a redox reaction. The ArcA/ArcB regulator of aerobic metabolism in Escherichia coli may use a different sensory mechanism. In two-component regulators, the sensor is located in the cytoplasmic membrane, whereas one-component regulators are located in the cytoplasm. Under most conditions, O can readily reach the cytoplasm and could provide the signal in the cytoplasm. The transcriptional regulator FNR of E. coli controls the expression of many genes required for anaerobic metabolism in response to O. Functional homologs of FNR are present in facultatively anaerobic Proteobacteria and presumably also in gram-positive bacteria. The target genes of FNR are mostly under multiple regulation by FNR and other regulators that respond to O, nitrate, or glucose. FNR represents a 'one-component' sensor/regulator and contains Fe for signal perception. In response to O availability, FNR is converted reversibly from the aerobic (inactive) state to the anaerobic (active) state. Experiments suggest that the Fe cofactor is bound by four essential cysteine residues. The O-triggered transformation between active and inactive FNR presumably is due to a redox reaction at the Fe cofactor, but other modes of interaction cannot be excluded. O seems to affect the site-specific DNA binding of FNR at target genes or the formation of an active transcriptional complex with RNA polymerase. [ABSTRACT FROM AUTHOR]

Availability of O is one of the most important regulatory signals in facultatively anaerobic bacteria. Various two- or one-component sensor/regulator systems control the expression of aerobic and anaerobic metabolism in response to O. Most of the sensor proteins contain heme or Fe as cofactors that interact with O either by binding or by a redox reaction. The ArcA/ArcB regulator of aerobic metabolism in Escherichia coli may use a different sensory mechanism. In two-component regulators, the sensor is located in the cytoplasmic membrane, whereas one-component regulators are located in the cytoplasm. Under most conditions, O can readily reach the cytoplasm and could provide the signal in the cytoplasm. The transcriptional regulator FNR of E. coli controls the expression of many genes required for anaerobic metabolism in response to O. Functional homologs of FNR are present in facultatively anaerobic Proteobacteria and presumably also in gram-positive bacteria. The target genes of FNR are mostly under multiple regulation by FNR and other regulators that respond to O, nitrate, or glucose. FNR represents a 'one-component' sensor/regulator and contains Fe for signal perception. In response to O availability, FNR is converted reversibly from the aerobic (inactive) state to the anaerobic (active) state. Experiments suggest that the Fe cofactor is bound by four essential cysteine residues. The O-triggered transformation between active and inactive FNR presumably is due to a redox reaction at the Fe cofactor, but other modes of interaction cannot be excluded. O seems to affect the site-specific DNA binding of FNR at target genes or the formation of an active transcriptional complex with RNA polymerase. [ABSTRACT FROM AUTHOR]

A new binding-protein-dependent transport system of Escherichia coli specific for L-arginine was characterized by genetic and biochemical means. The system is encoded by five adjacent genes, artPIQMJ (art standing for arginine transport), which are organized in two transcriptional units (artPIQM and artJ). The artI and artJ gene products (ArtI and ArtJ) are periplasmic binding proteins with sequence similarity to binding proteins for polar (basic) amino acids. The artQ, artM and artP products are similar to the transmembraneous proteins and the ATPase of binding-protein-dependent carriers. The mature ArtI and J proteins were localized in the periplasm and lacked signal peptides of 19 amino acid residues. ArtI and ArtJ were isolated from overproducing strains. ArtJ specifically binds L-arginine with high affinity and overproduction of ArtJ stimulated L-arginine uptake by the bacteria. The substrate for ArtI is not known, and isolated ArtI did not bind common amino acids, various basic uncommon amino acids or amines. It is concluded that the artPIQM artJ genes encode a third arginine-uptake system in addition to the known argT hisJQMP system of Salmonella typhimurium and E. coli and the arginine (-ornithine) carrier (aps) of E. coli. [ABSTRACT FROM AUTHOR]