Analyzed Two Component Systems modules.

<p>Model A represents a prototypical TCS. Model B represents a TCS with a SK-binding third component (TC_SK). Model C represents a TCS with a RR-binding third component (TC_RR). SK: sensor kinase; RR: response regulator; SKP: phosphorylated SK; RRP: phosphorylated RR; Ph: alternative phosphatase that dephosphorylates RRP; SKRR: dead-end complex, resulting from the binding of SK and RR; SKPRR: protein complex formed by the binding of SKP and RR; SKRRP: protein complex formed by the binding of SK and RRP; PhRRP: protein complex formed by the binding of Ph and RRP; SKTC and RRPTC: protein complexes formed by the binding of the third component to SK and RRP, respectively; (k₁, …, k₁₈): kinetic constants of the individual reactions. For simplicity, ATP and the release of inorganic phosphate are omitted. To analyze TCS modules with monofunctional sensors, k₈ is set to 0. To analyze TCS modules with bifunctional sensors, k₈ is set to be different from 0.