A novel Archael type CO sensing regulator: RchA

Abstract

Carbon monoxide (CO) is a notorious toxic gas that can cause sometimes suffocation by poisoning. This toxicity comes from its strong affinity to metals. Due to its strong affinity to haemoglobin, it can block tissue oxygenation and also inhibit mitochondrial electron transport chain by binding cytochrome. On the other hand, some microorganisms are able to get benefit from CO. CO is not only a key factor for autotrophic pathway such as methanogenesis and acetogenesis but an energy source for carboxydotrophic bacteria like Carboxydothermus hydrogenoformans and Rhodospirillium rubrum. The carboxydotrophic bacteria encode energy conserving hydrogenase gene cluster (mch) linked to carbon monoxide dehydrogenase (CODH) in their genome and CooA type CO sensing regulator is responsible for timely expression of this cluster in response to CO. CooA can sense the presence of CO through heme, and CO binding to heme causes conformational change that leads to transcriptional activation of CODH-mch cluster. RcoM is another CO-sensing regulator from Burkholderia xenovorans and similar to CooA in that it takes advantage of heme for CO binding. Thermococcus onnurineus NA1 was reported to harbor CODH-mch cluster essential for CO-dependent growth. Transcriptional and translational regulation of this cluster in response to CO was confirmed by RT-qPCR and western blotting but there is no CO sensing regulator in the genome homologous to Cibit mitochondrial electron transport chain by binding cytochrome. On the other hand, some microorganisms are able to get benefit from CO. CO is not only a key factor for autotrophic pathway such as methanogenesis and acetogenesis but an energy source for carboxydotrophic bacteria like Carboxydothermus hydrogenoformans and Rhodospirillium rubrum. The carboxydotrophic bacteria encode energy conserving hydrogenase gene cluster (mch) linked to carbon monoxide dehydrogenase (CODH) in their genome and CooA type CO sensing regulator is responsible for timely expression of this cluster in response to CO. CooA can sense the presence of CO through heme, and CO binding to heme causes conformational change that leads to transcriptional activation of CODH-mch cluster. RcoM is another CO-sensing regulator from Burkholderia xenovorans and similar to CooA in that it takes advantage of heme for CO binding. Thermococcus onnurineus NA1 was reported to harbor CODH-mch cluster essential for CO-dependent growth. Transcriptional and translational regulation of this cluster in response to CO was confirmed by RT-qPCR and western blotting but there is no CO sensing regulator in the genome homologous to C