title: A structure-based interpretation of E.coli GrpE thermodynamic properties.
abstract: GrpE is the nucleotide exchange factor for the Escherichia coli molecular chaperone DnaK, the prokaryotic homologue of Hsp70. Thermodynamic properties of GrpE structural domains were characterized by examining a number of structural and point mutants using circular dichroism, differential scanning calorimetry and analytical ultracentrifugation. These structural domains are the long paired N-terminal helices, the central four-helix bundle, and the C-terminal compact beta-domains. We show that the central four-helix bundle (t(m) approximately 75 degrees C) provides a stable platform for the association of the long paired N-terminal helices (t(m) approximately 50 degrees C), which can then function as a temperature sensor. The stability of the N-terminal helices is linked to the presence of the C-terminal compact beta-domains of GrpE, providing a potential mechanism for coupling of DnaK-binding activity of GrpE with temperature. On the basis of our thermodynamic analysis of E.coli GrpE, we present a structure-based model for the melting properties of the nucleotide exchange factor, wherein the long paired helices function as a molecular thermocouple.
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C068113:GrpE protein, Bacteria; C489400:GrpE protein, E coli; D006360:Heat-Shock Proteins