A bacterial signal transduction phosphorelay in the methanogenic archaeon Methanosarcina acetivorans

Signal transduction via two-component systems is a powerful tool for microorganisms to respond to environmental changes. Histidine kinases originating from Bacteria are the most common signaling enzymes and are also present in Archaea, but not in all phyla. A total of 124 bacterial-type histidine kinases and/or regulators were identified in a screen of 149 Euryarchaeota genomes, but little is known about the signal transfer and molecular regulation of these systems (1). In this work, the hybrid kinase MA4377 from the methanogenic archaeon Methanosarcina acetivorans was investigated (2, 3). MA4377 is a multidomain protein resembling a bacterial-type histidine kinase with two additional receiver domains at the C-terminus. Recombinant protein was employed to investigate the intra- and intermolecular phosphorelay in vitro. The kinase displays autophosphorylation activity of histidine residue 497. While no intramolecular phosphorelay was observed, the CheY-like receiver protein MA4376 was identified as part of the multi-component system that also seems to include the Msr-type transcription factor MA4375. This study reveals the presence and in vitro function of a bacterial-type hybrid histidine kinase integrated into an archaeal phosphorelay system. ImportanceSignal transduction enables organisms to rapidly react to changes in their surroundings. Different systems containing one-, two- or multiple-components are employed to sense and react to environmental changes. Most commonly, external perceived stimuli are converted into internal signals through protein phosphorylation. These systems are found in all domains of life but understood at different levels of complexity, the least being those from the domain of Archaea. By better elucidating the function of these early signal transduction systems, we will gain insight and understanding of the selection pressures on signal transduction pathways, and their evolution within the Archaea.