| Modification Notes |
MAP kinase cascades, consisting of a mitogen-activated protein kinase (also called ERK, for extracellular regulated kinase) and one or more upstream regulatory kinases (MAPKKs), play an integral role in signal transduction. One of the best characterized MAP kinase pathways is the yeast pheromone response pathway (1). Extracellular pheromones bind to the receptors Ste2 and Ste3, which couple to a heterotrimeric G protein (2). The G protein consists of å, ß and g subunits, respectively designated Gpa1 (also called SCG1, CDC70 or DAC1), Ste4 and Ste18 (3,4). Activation of this G protein leads to the activation of the MAPKKK Ste11, which then activates the MAPKK Ste7 (5). Activated Ste7 phosphorylates the MAP kinases Fus3 (also called Dac2) and Kss1 (6). These MAP kinases activate the transcription factor Ste12, which upregulates mating-specific genes and Far1, which is involved in cell cycle arrest (7,8). |
