Structural and functional analysis of the SAM domain in protein kinase signaling.
Published: 2005
Language: eng
Number of pages: 234
Description: Protein kinases (PKs) are important components of many intracellular signal-transduction pathways. These enzymes are capable of catalyzing the transfer of the gamma phosphate of ATP to a hydroxyl group in a suitable substrate and thus affecting the activity of this target protein. The regulation of PK activity is crucial to the proper development and maintenance of eukaryotic organisms. Here, I explore the regulation of a subset of PKs that contain a Sterile Alpha Motif (SAM) domain. The SAM domain is a conserved protein module commonly found in many signaling molecules including scaffolding proteins, adaptor molecules, and PKs. In the yeast Ste11 serine/threonine PK, the N-terminal SAM domain is required for Ste11 dependent signaling. Here, I demonstrate that the Ste11 SAM domain specifically binds to the SAM domain of its substrate, Ste50, and that this interaction is required for in vivo function. Structural and mutagenesis studies identify specific residues within the Ste11 and Ste50 SAM domains that are functionally important in mediating this interaction. In a similar structure-function based approach using the mouse EphA4 receptor tyrosine kinase I identified a highly conserved tyrosine residue within the C-terminal SAM domain that negatively regulates EphA4 signaling. This analysis also led to the identification of a highly conserved tyrosine residue within the kinase domain of Eph receptors, termed the bypass residue, whose chemical nature and conformation appear to be important in controlling Eph kinase activity. These results increase our understanding of the molecular mechanisms by which PKs are regulated. Furthermore, the knowledge gained with respect to the biochemical properties of specific SAM domains, and their role in regulating PK signaling, increases our general understanding of how SAM domain-containing proteins function to mediate cellular communication.
Notes: Source: Dissertation Abstracts International, Volume: 66-10, Section: B, page: 5248.

Thesis (Ph.D.)--University of Toronto, 2005.

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