Feedback regulation of map kinase signal pathways

Ste7 is a MEK (MAPK/ERK kinase) family member that functions in the pheromone induced mating response pathway of Saccharomyces cerevisiae. We analysed the catalytic competence and in vivo function of Ste7 variants that have alterations of stimulatory and feedback phosphorylation sites. These analyses led us to unanticipated insights into two separate feedback mechanisms that impede the output of the mating response MAPK activation pathway.