A GrpE mutant containing the NH(2)-terminal "tail" region is able to displace bound polypeptide substrate from DnaK.
A key feature to the dimeric structure for the GrpE heat shock protein is the pair of long helices at the NH(2)-terminal end followed by a presumable extended segment of about 30 amino acids from each monomer. We have constructed a GrpE deletion mutant protein that contains only the unique tail portion (GrpE1-89) and another that is missing this region (GrpE88-197). Circular dichroism analysis shows that the GrpE1-89 mutant still contains one-third percent alpha-helical secondary structure. Using an assay that measures bound peptide to DnaK we show that the GrpE1-89 is able to lower the amount of bound peptide, whereas GrpE88-197 has no effect. Additionally, when the same peptide binding assay is carried out with the COOH-terminal domain of DnaK, the full-length GrpE and the two GrpE deletion mutants show little to no effect on peptide release. Furthermore, the GrpE88-197 mutant is able to enhance the off-rate of nucleotide from DnaK and the 1-89 mutant has no effect on the nucleotide release. Similar results of nucleotide release are observed with the NH(2)-terminal ATPase domain mutant of DnaK. The results presented show directly that there is interaction between the GrpE protein's "tail" region and the substrate COOH-terminal peptide binding domain of DnaK, although the effect is only fully manifest with an intact full-length DnaK molecule.
Mehl
A F
AF
Department of Chemistry, Knox College, 2 East South Street, Galesburg, Illinois 61401, USA. amehl@knox.edu
Heskett
L D
LD
Neal
K M
KM
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D002942:Circular Dichroism; D017931:DNA Primers / Q000235:genetics; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D015870:Gene Expression; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D013379:Substrate Specificity
D001426:Bacterial Proteins; D017931:DNA Primers; D029968:Escherichia coli Proteins; C068113:GrpE protein, Bacteria; C489400:GrpE protein, E coli; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli