FIG. 1.

MAPK module. (A) The MAPK module lies at the heart of many signalling pathways in eukaryotes. An input signal leads to activation of the MAPK cascade, which then generates an output response. (B) The MAPK cascade consists of MAPKKK (MEKK), MAPKK (MEK), and MAPK (ERK) (see the text for details). A receptor is activated in response to an extracellular signal, which leads to activation of the MAPK cascade (see the text for details). The activated MAPK phosphorylates substrates, some of which include transcriptional activators, resulting in altered patterns of gene expression and protein activity.