McpS is the chemoreceptor for succinate. A, agarose-plug assays of P. putida KT2440 and a mutant deficient in pp4658 (mcpS) with succinate and toluene (positive control). B, domain prediction of McpS according to SMART (14): TM, transmembrane region; HAMP, linker domain; MA, methyl-accepting domain. C, consensus secondary structure prediction of McpS-LBD using NPSA (37).