Mechanisms for redox control of gene expression

This review discusses various mechanisms that regulatory proteins use to co ntrol gene expression in response to alterations in redox. The transcriptio n factor SoxR contains stable [2Fe-2S] centers that promote transcription a ctivation when oxidized. FNR contains [4Fe-4S] centers that disassemble und er oxidizing conditions, which affects DNA-binding activity. FixL is a hist idine sensor kinase that utilizes heme as a cofactor to bind oxygen, which affects its autophosphorylation activity. NifL is a flavoprotein that conta ins FAD as a redox responsive cofactor. Under oxidizing conditions, NifL bi nds and inactivates NifA, the transcriptional activator of the nitrogen fix ation genes. OxyR is a transcription factor that responds to redox by break ing or forming disulfide bonds that affect its DNA binding activity. The ab ility of the histidine sensor kinase ArcB to promote phosphorylation of the response regulator ArcA is affected by multiple factors such as anaerobic metabolites and the redox state of the membrane. The global regulator of an aerobic gene expression in a-purple proteobacteria, RegB, appears to direct ly monitor respiratory activity of cytochrome oxidase. The aerobic represso r of photopigment synthesis, CrtJ, seems to contain a redox responsive cyst eine. Finally, oxygen-sensitive rhizobial NifA proteins presumably bind a m etal cofactor that senses redox. The functional variability of these regula tory proteins demonstrates that prokaryotes apply many different mechanisms to sense and respond to alterations in redox.