title: Examination of the dynamic assembly equilibrium for E. coli ClpB.
abstract: Escherichia coli ClpB is a heat shock protein that belongs to the AAA+ protein superfamily. Studies have shown that ClpB and its homologue in yeast, Hsp104, can disrupt protein aggregates in vivo. It is thought that ClpB requires binding of nucleoside triphosphate to assemble into hexameric rings with protein binding activity. In addition, it is widely assumed that ClpB is uniformly hexameric in the presence of nucleotides. Here we report, in the absence of nucleotide, that increasing ClpB concentration leads to ClpB hexamer formation, decreasing NaCl concentration stabilizes ClpB hexamers, and the ClpB assembly reaction is best described by a monomer, dimer, tetramer, hexamer equilibrium under the three salt concentrations examined. Further, we found that ClpB oligomers exhibit relatively fast dissociation on the time scale of sedimentation. We anticipate our studies on ClpB assembly to be a starting point to understand how ClpB assembly is linked to the binding and disaggregation of denatured proteins.
authors: Department of Chemistry, University of Alabama at Birmingham, Birmingham, Alabama, 35294.
authors: JiaBei
authors: J
authors: Lin
authors: Department of Chemistry, University of Alabama at Birmingham, Birmingham, Alabama, 35294.
authors: Aaron L
authors: AL
authors: Lucius
mesh_terms: D049071:Endopeptidase Clp; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D055503:Protein Multimerization; D058767:Protein Unfolding; D012965:Sodium Chloride; D013816:Thermodynamics
chemical_list: D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D012965:Sodium Chloride; D049071:Endopeptidase Clp; C069775:ClpB protein, E coli
keywords: AAA+ motor proteins; SedAnal; Sedfit; analytical ultracentrifugation; chaperones; hexamer; kinetics; protein quality control; protein unfoldases; thermodynamics