REDOX CONTROL OF TRANSCRIPTION - SENSORS, RESPONSE REGULATORS, ACTIVATORS AND REPRESSORS

In a growing number of cases, transcription of specific genes is known to be governed by oxidation or reduction of electron carriers with wh ich the gene products interact. The biological function of such contro l is to activate synthesis of appropriate redox proteins, and to repre ss synthesis of inappropriate ones, in response to altered availabilit y of specific electron sources and sinks. In prokaryotic systems this control appears to operate by two general classes of mechanism: by two -component regulation involving protein phosphorylation on histidine a nd aspartate; and by direct oxidation-reduction of gene repressors or activators. For the first class, termed 'two-component redox regulatio n', the term 'redox sensor' is proposed for any electron carrier that becomes phosphorylated upon oxidation or reduction and thereby control s phosphorylation of specific response regulators, while the term 'red ox response regulator' is proposed for the corresponding sequence-spec ific DNA-binding protein that controls transcription as a result of it s phosphorylation by one or more redox sensors. For the second class o f redox regulatory mechanism, the terms 'redox activator protein' and 'redox repressor protein' are proposed for single proteins containing both electron transfer and sequence-specific DNA-binding domains. The structure, function and biological distribution of these components ar e discussed.