This protein, TorS, is part of a regulatory system for the torCAD operon that encodes the pterin molybdenum cofactor-containing enzyme trimethylamine-N-oxide (TMAO) reductase (TorA), a cognate chaperone (TorD), and a penta-haem cytochrome (TorC). TorS works together with the inducer-binding protein TorT and the response regulator TorR. TorS contains histidine kinase ATPase (pfam02518), HAMP (pfam00672), phosphoacceptor (pfam00512), and phosphotransfer (pfam01627) domains and a response regulator receiver domain (pfam00072). [Signal transduction, Two-component systems]