title: CbpA, a DnaJ homolog, is a DnaK co-chaperone, and its activity is modulated by CbpM.
abstract: The DnaK chaperone system, consisting of DnaK, DnaJ, and GrpE, remodels and refolds proteins during both normal growth and stress conditions. CbpA, one of several DnaJ analogs in Escherichia coli, is known to function as a multicopy suppressor for dnaJ mutations and to bind nonspecifically to DNA and preferentially to curved DNA. We found that CbpA functions as a DnaJ-like co-chaperone in vitro. CbpA acted in an ATP-dependent reaction with DnaK and GrpE to remodel inactive dimers of plasmid P1 RepA into monomers active in P1 DNA binding. Additionally, CbpA participated with DnaK in an ATP-dependent reaction to prevent aggregation of denatured rhodanese. The cbpA gene is in an operon with an open reading frame, yccD, which encodes a protein that has some homology to DafA of Thermus thermophilus. DafA is a protein required for the assembly of ring-like particles that contain trimers each of T. thermophilus DnaK, DnaJ, and DafA. The E. coli YccD was isolated because of its potential functional relationship to CbpA. Purified YccD specifically inhibited both the co-chaperone activity and the DNA binding activity of CbpA, suggesting that YccD modulates the activity of CbpA. We named the product of the yccD gene CbpM for "CbpA modulator."
authors.affiliation: Laboratory of Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Chi
authors.initials: C
authors.lastname: Chae
authors.forename: Suveena
authors.initials: S
authors.lastname: Sharma
authors.forename: Joel R
authors.initials: JR
authors.lastname: Hoskins
authors.forename: Sue
authors.initials: S
authors.lastname: Wickner
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000378:metabolism* / Q000502:physiology; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism; D018832:Molecular Chaperones; D016366:Open Reading Frames; D009876:Operon; D010957:Plasmids / Q000235:genetics; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D013884:Thiosulfate Sulfurtransferase / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C490083:CbpA protein, bacteria; C492508:CbpM protein, E coli; D004268:DNA-Binding Proteins; C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; C068113:GrpE protein, Bacteria; C489400:GrpE protein, E coli; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D011506:Proteins; D000255:Adenosine Triphosphate; D004247:DNA; D013884:Thiosulfate Sulfurtransferase; C063842:dnaK protein, E coli