Yerko V, Sulea T, Ekiel I, Harcus D, Baardsnes J, Cygler M, Whiteway M, Wu C

The Ste5 protein forms a scaffold that associates and regulates the components of the MAP kinase cascade that controls mating-pheromone mediated signaling in the yeast Saccharomyces cerevisiae. Although it is known that the MEKK of the pathway, Ste11, associates with Ste5, details of this interaction have not been established. We ...

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have identified a Ras-binding-domain-like (RBL) region in the Ste11 protein that is required specifically for the kinase to function in the mating pathway. This module is structurally related to domains in other proteins that mediate Ras-MAPKKK associations; however this RBL module does not interact with Ras, but rather binds the PH domain of the Ste5 scaffold. Structural and functional studies suggest that the key role of this PH domain is to mediate the Ste5-Ste11 interaction. Overall, these two evolutionarily conserved modules interact with each other through a unique interface, and thus in the pheromone pathway the structural context of the RBL domain contribution to kinase activation has been shifted through a change of its interaction partner from Ras to a PH domain.

Date: Dec. 14, 2012

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