Signal transduction systems in the methanogenic archaeon Methanosarcina acetivorans
Methane is a greenhouse gas that is becoming increasingly important as a new source of energy and is produced by methanogenic Archaea. These group of Archaea are able to use a variety of different substrates to produce methane. The presence of these substrates have to be detected by the organism. In the domain of Bacteria such processes are regulated by two-component systems (TCS) consisting of a sensor kinase and a response regulator. In methanogenic Archaea like Methanosarcina acetivorans not much is known about these systems. The first examples for sensor kinases in methanogenic Archaea are the proteins MsmS and RdmS, which consist of alternating PAS- and GAF-domains and a C-terminal ATPase-domain. It has been shown that the second GAF-domain of both proteins contains a covalently bound heme cofactor and that the autophosphorylation activity is influenced by the proteins’ redox state. MsmS is most likely phosphorylated at a serine/threonine or tyrosine residue whereas RdmS is phosphorylated at a tyrosine residue. Another sensor kinase is the membrane-bound hybrid kinase MA4377 which differs in its constitution and autophosphorylation activity from MsmS and RdmS. It could be shown that MA4377 is phosphorylated at a histidine residue independently of the proteins’ redox state.
The genes msmS, rdmS and MA4377 are localized upstream of three regulator proteins (MsrG, MsrF, MsrC) and the corrinoid-methyltransferases MtsH, MtsD and MtsF, which are important for metabolizing dimethyl sulfide in methanogenesis. This leads to the suggestion that the sensor kinases together with the regulators form two-/multi-component systems and are involved in the regulation of the mts-genes.
In this project we investigate the intramolecular signal transduction of the sensor kinases as well as the intermolecular interaction with the regulator proteins and their binding to the mts promoter regions. Altogether we would like to contribute with our work to the understanding of archaeal signal transduction and to methanogenic physiology in particular.