Exploring the Binding Site Structure of the PPARγ Ligand-Binding Domain by Computational Solvent Mapping

Shu-Hsien Sheu, Taner Kaya,§ David J. Waxman, and Sandor Vajda*
Departments of Biomedical Engineering, Chemistry, and Biology, Boston University, 44 Cummington Street, Boston, Massachusetts 02215
Biochemistry, 2005, 44 (4), pp 1193–1209
DOI: 10.1021/bi048032c
Publication Date (Web): December 30, 2004
Copyright © 2005 American Chemical Society

Abstract

Abstract Image

Solvent mapping moves molecular probes, small organic molecules containing various functional groups, around the protein surface, finds favorable positions, clusters the conformations, and ranks the clusters based on the average free energy. Using at least six different solvents as probes, the probes cluster in major pockets of the functional site, providing detailed and reliable information on the amino acid residues that are important for ligand binding. Solvent mapping was applied to 12 structures of the peroxisome proliferator activated receptor γ (PPARγ) ligand-binding domain (LBD), including 2 structures without a ligand, 2 structures with a partial agonist, and 8 structures with a PPAR agonist bound. The analysis revealed 10 binding “hot spots”, 4 in the ligand-binding pocket, 2 in the coactivator-binding region, 1 in the dimerization domain, 2 around the ligand entrance site, and 1 minor site without a known function. Mapping is a major source of information on the role and cooperativity of these sites. It shows that large portions of the ligand-binding site are already formed in the PPARγ apostructure, but an important pocket near the AF-2 transactivation domain becomes accessible only in structures that are cocrystallized with strong agonists. Conformational changes were seen in several other sites, including one involved in the stabilization of the LBD and two others at the region of the coactivator binding. The number of probe clusters retained by these sites depends on the properties of the bound agonist, providing information on the origin of correlations between ligand and coactivator binding.

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History

  • Published In Issue February 01, 2005
  • Received September 12, 2004
    Revised Manuscript Received October 30, 2004

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