Abstract #8

Adaptor protein Ste50p links the Ste11p MEKK to the HOG pathway through plasma membrane association. Cunle Wu¹, Gregor Jansen², Jianchun Zhang¹, David Y. Thomas², Malcolm Whiteway^1,3. 1) Eukaryotic Genetics Group, Biotechnology Research Institute, Montreal, QC, Canada; 2) Department of Biochemistry, McGill University, Montreal, QC, Canada; 3) Department of Biology, McGill University, Montreal QC, Canada.
   In a variety of yeast cellular pathways, the Ste50p protein regulates the kinase function of the MEKK Ste11p. Both Ste11p and Ste50p contain SAM domains; these are interchangeable, and can be replaced by other protein interacting modules. Furthermore, the function of the RA-like domain of Ste50p can be mimicked by a plasma membrane recruiting signal, and direct plasma membrane targeting of Ste11p bypasses the requirement of Ste50p for Ste11p function. Thus the regulatory role of Ste50p requires both the N-terminal SAM domain to bind Ste11p, and the C-terminal RA-like domain to direct kinase localization. We have identified Opy2p, an integral membrane protein that can interact with Ste50p, as a new component in the Sho1p-Ste11p/Ste50p signalling branch of the HOG pathway. We propose that Opy2p can serve as a membrane anchor for the Ste50p/Ste11p module in the activation of the HOG pathway.

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