O-2-SENSING AND O-2-DEPENDENT GENE-REGULATION IN FACULTATIVELY ANAEROBIC-BACTERIA

Citation
G. Unden et al., O-2-SENSING AND O-2-DEPENDENT GENE-REGULATION IN FACULTATIVELY ANAEROBIC-BACTERIA, Archives of microbiology, 164(2), 1995, pp. 81-90
Citations number
112
Categorie Soggetti
Microbiology
Journal title
ISSN journal
03028933
Volume
164
Issue
2
Year of publication
1995
Pages
81 - 90
Database
ISI
SICI code
0302-8933(1995)164:2<81:OAOGIF>2.0.ZU;2-4
Abstract
Availability of O-2 is one of the most important regulatory signals in facultatively anaerobic bacteria. Various two- or one-component senso r/regulator systems control the expression of aerobic and anaerobic me tabolism in response to O-2. Most of the sensor proteins contain heme or Fe as cofactors that interact with O-2 either by binding or by a re dox reaction. The ArcA/ArcB regulator of aerobic metabolism in Escheri chia coli may use a different sensory mechanism. In two-component regu lators, the sensor is located in the cytoplasmic membrane, whereas one -component regulators are located in the cytoplasm . Under most condit ions, O-2 can readily reach the cytoplasm and could provide the signal in the cytoplasm. The transcriptional regulator FNR of E. coli contro ls the expression of many genes required for anaerobic metabolism in r esponse to O-2. Functional homologs of FNR are present in facultativel y anaerobic Proteobacteria and presumably also in gram-positive bacter ia. The target genes of FNR are mostly under multiple regulation by FN R and other regulators that respond to O-2, nitrate, or glucose. FNR r epresents a 'one-component' sensor/regulator and contains Fe for signa l perception. In response to O-2 availability, FNR is converted revers ibly 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-2-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-2 seems to affe ct the site-specific DNA binding of FNR at target genes or the formati on of an active transcriptional complex with RNA polymerase.