GrpE accelerates peptide binding and release from the high affinity state of DnaK.
The Escherichia coli nucleotide exchange factor GrpE accelerates the rate of ADP dissociation from high affinity ADP-DnaK, thus enabling ATP binding and transition to the low affinity state. We show here that GrpE, in the absence of ATP, accelerates the rates of the forward and reverse reaction ADP-DnaK-P right harpoon over left harpoon ADP-DnaK + P, where P denotes peptide substrate. Specifically, the binding of GrpE to an ADP-DnaK-P (or DnaK-P) complex increases koff and kon by approximately 200-fold and approximately 60-fold, respectively. The results are consistent with a GrpE- induced conformational change in the C-terminal polypeptide binding domain of an ADP-DnaK molecule, which results in a unique low affinity intermediate from which peptide can dissociate. A simulation of peptide dissociation from DnaK as a function of the [ATP] / [ADP] ratio shows that GrpE induced peptide dissociation from ADP-DnaK is important at elevated cellular concentrations of ADP, which typically occur upon stress.
Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, Louisiana 71130-3932, USA.
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D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D003619:Dansyl Compounds; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D007700:Kinetics; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence
D001426:Bacterial Proteins; D003619:Dansyl Compounds; D029968:Escherichia coli Proteins; C068113:GrpE protein, Bacteria; C489400:GrpE protein, E coli; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D010455:Peptides; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C063842:dnaK protein, E coli