1PL5

Crystal Structure Analysis of the Sir4p C-terminal Coiled Coil

Summary for 1PL5

• Entry DOI: 10.2210/pdb1pl5/pdb
• Descriptor: Regulatory protein SIR4 (2 entities in total)
• Functional Keywords: parallel coiled coil homodimer, dna binding protein-transcription complex, dna binding protein/transcription
• Biological source: Saccharomyces cerevisiae (baker's yeast)
• Cellular location: Nucleus: P11978
• Total number of polymer chains: 2
• Total formula weight: 31917.77

Authors

Murphy, G.A.,Spedale, E.J.,Powell, S.T.,Pillus, L.,Schultz, S.C.,Chen, L. (deposition date: 2003-06-06, release date: 2004-06-01, Last modification date: 2024-02-14)

Primary citation

Murphy, G.A.,Spedale, E.J.,Powell, S.T.,Pillus, L.,Schultz, S.C.,Chen, L.
The Sir4 C-terminal coiled coil is required for telomeric and mating type silencing in Saccharomyces cerevisiae.
J.Mol.Biol., 334:769-780, 2003

PubMed Abstract: Saccharomyces cerevisiae Sir4p plays important roles in silent chromatin at telomeric and silent mating type loci. The C terminus of Sir4p (Sir4CT) is critical for its functions in vivo because over-expression or deletion of Sir4CT fragments disrupts normal telomeric structure and abolishes the telomere position effect. The 2.5A resolution X-ray crystal structure of an Sir4CT fragment (Sir4p 1217-1358) reveals a 72 residue homodimeric, parallel coiled coil, burying an extensive 3600A(2) of surface area. The crystal structure is consistent with results of protein cross-linking and analytical ultracentrifugation results demonstrating that Sir4CT exists as a dimer in solution. Disruption of the coiled coil in vivo by point mutagenesis results in total derepression of telomeric and HML silent mating marker genes, suggesting that coiled coil dimerization is essential for Sir4p-mediated silencing. In addition to the coiled coil dimerization interface (Sir4CC interface), a crystallographic interface between pairs of coiled coils is significantly hydrophobic and buries 1228A(2) of surface area (interface II). Remarkably, interface II mutants are deficient in telomeric silencing but not in mating type silencing in vivo. However, point mutants of interface II do not affect the oligomerization state of Sir4CT in solution. These results are consistent with the hypothesis that interface II mimics a protein interface between Sir4p and one of its protein partners that is essential for telomeric silencing but not mating type silencing.

PubMed: 14636601
DOI: 10.1016/j.jmb.2003.09.066

Experimental method

X-RAY DIFFRACTION (2.5 Å)