1YWT

Crystal structure of the human sigma isoform of 14-3-3 in complex with a mode-1 phosphopeptide

Summary for 1YWT

• Entry DOI: 10.2210/pdb1ywt/pdb
• Related: 1QJA 1QJB
• Descriptor: 14-3-3 protein sigma, synthetic optimal phosphopeptide (mode-1), CALCIUM ION, ... (4 entities in total)
• Functional Keywords: protein-phosphopeptide complex, 14-3-3, signaling protein-de novo protein complex, signaling protein/de novo protein
• Biological source: Homo sapiens (human); More
• Cellular location: Cytoplasm: P31947
• Total number of polymer chains: 4
• Total formula weight: 58487.29

Authors

Wilker, E.W.,Grant, R.A.,Artim, S.C.,Yaffe, M.B. (deposition date: 2005-02-18, release date: 2005-03-01, Last modification date: 2024-10-09)

Primary citation

Wilker, E.W.,Grant, R.A.,Artim, S.C.,Yaffe, M.B.
A structural basis for 14-3-3sigma functional specificity.
J.Biol.Chem., 280:18891-18898, 2005

PubMed Abstract: The 14-3-3 family of proteins includes seven isotypes in mammalian cells that play numerous diverse roles in intracellular signaling. Most 14-3-3 proteins form homodimers and mixed heterodimers between different isotypes, with overlapping roles in ligand binding. In contrast, one mammalian isoform, 14-3-3sigma, expressed primarily in epithelial cells, appears to play a unique role in the cellular response to DNA damage and in human oncogenesis. The biological and structural basis for these 14-3-3sigma-specific functions is unknown. We demonstrate that endogenous 14-3-3sigma preferentially forms homodimers in cells. We have solved the x-ray crystal structure of 14-3-3sigma bound to an optimal phosphopeptide ligand at 2.4 angstroms resolution. The structure reveals the presence of stabilizing ring-ring and salt bridge interactions unique to the 14-3-3sigma homodimer structure and potentially destabilizing electrostatic interactions between subunits in 14-3-3sigma-containing heterodimers, rationalizing preferential homodimerization of 14-3-3sigma in vivo. The interaction of the phosphopeptide with 14-3-3 reveals a conserved mechanism for phospho-dependent ligand binding, implying that the phosphopeptide binding cleft is not the critical determinant of the unique biological properties of 14-3-3sigma. Instead, the structure suggests a second ligand binding site involved in 14-3-3sigma-specific ligand discrimination. We have confirmed this by site-directed mutagenesis of three sigma-specific residues that uniquely define this site. Mutation of these residues to the alternative sequence that is absolutely conserved in all other 14-3-3 isotypes confers upon 14-3-3sigma the ability to bind to Cdc25C, a ligand that is known to bind to other 14-3-3 proteins but not to sigma.

PubMed: 15731107
DOI: 10.1074/jbc.M500982200

Experimental method

X-RAY DIFFRACTION (2.4 Å)