. "\"Catalysis of the phosphorylation of a histidine residue in response to detection of an extracellular signal such as a chemical ligand or change in environment, to initiate a change in cell state or activity. The two-component sensor is a histidine kinase that autophosphorylates a histidine residue in its active site. The phosphate is then transferred to an aspartate residue in a downstream response regulator, to trigger a response.\" [GOC:bf, GOC:mcc, PMID:10966457, PMID:20223701, PMID:9191038]" . . "phosphorelay sensor kinase activity" . "EC:2.7.3.-" . . . "two-component sensor molecule" . "two-component sensor activity" . "two-component system sensor activity" .