FIG. 4.

Representation of interaction between two signal transduction pathways. Upon external stimulation, the signaling molecule (usually the stimulus itself) binds to the outer membrane receptor proteins. The structural changes that these proteins undergo trigger the phosphorylation of kinases which are activated to trigger the transfer of signal to the transcription factors that bind to specific binding targets upstream of genes, thereby regulating their expression. Such two-component signal transduction systems have so far been studied in isolation, but recent -omic approaches have provided ample evidence for the existence of interactions between these systems.