Phosphorelay signaling in yeast in response to changes in osmolarity

In the yeast, Saccharomyces cerevesiae, phosphorelay signaling systems that involve a three-step His-Asp-His-Asp phosphotransfer are involved in transmitting signals in response to cellular stress. The animation shows one example of such a phosphorelay system involved in yeast responses to changes in osmolarity. Under conditions of low osmolarity, a histidine-aspartate phosphorelay pathway transmits information that deactivates one signaling pathway and activates gene expression through another pathway. In response to high osmolarity, the Sln1 kinase that initiates the phosphorelay is inhibited and the Hog1 mitogen-activated protein kinase cascade is active.