title: A water mediated electrostatic interaction gives thermal stability to the "tail" region of the GrpE protein from E. coli.
abstract: The GrpE protein from E. coli is a homodimer with an unusual structure of two long paired alpha-helices from each monomer interacting in a parallel arrangement to form a "tail" at the N-terminal end. Using site-directed mutagenesis, we show that there is a key electrostatic interaction involving R57 (mediated by a water molecule) that provides thermal stability to this "tail" region. The R57A mutant showed a drop in T (m) of 8.5 degrees C and a smaller DeltaH (u) (unfolding) compared to wild-type for the first unfolding transition, but no significant decrease in dimer stability as shown through equilibrium analytical ultracentrifugation studies. Another mutant (E94A) at the dimer interface showed a decrease in DeltaH (u )but no drop in T (m) for the second unfolding transition and a slight increase in dimer stability.
authors.affiliation: Department of Chemistry, Knox College, Galesburg, IL 61401, USA. amehl@knox.edu
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Mehl
authors.forename: Borries
authors.initials: B
authors.lastname: Demeler
authors.forename: Afaq
authors.initials: A
authors.lastname: Zraikat
mesh_terms: D002942:Circular Dichroism; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006360:Heat-Shock Proteins / Q000737:chemistry*; D006358:Hot Temperature; D008958:Models, Molecular; D008968:Molecular Conformation; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012492:Salts / Q000737:chemistry; D055672:Static Electricity; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D029968:Escherichia coli Proteins; C489400:GrpE protein, E coli; D006360:Heat-Shock Proteins; D012492:Salts; D014867:Water