title: D-peptide ligands for the co-chaperone DnaJ.
abstract: The molecular chaperone DnaK, the Hsp70 homolog of Escherichia coli, binds hydrophobic polypeptide segments in extended conformation. The co-chaperone DnaJ (Hsp40) has been reported to bind native and denatured proteins as well as peptides. We tested pseudo-peptides of D-amino acids as ligands for both chaperones. In comparison to the parent all-L peptide, these mimetics had either enantiomorphic side chain positions combined with retained main chain direction (normal all-D peptide) or unchanged side chain topology together with reverse direction of the peptide backbone (retro all-D peptide). The peptides were labeled with acrylodan (a), and their binding to DnaK and DnaJ was monitored by the accompanying increase in fluorescence intensity. The parent all-L peptide a-CALLLSAARR bound to both DnaK (Kd = 0.1 microM) and DnaJ (Kd = 9.2 microM). In contrast, the normal all-D and retro all-D peptides did not bind to DnaK; they bound, however, to DnaJ with Kd values of 6.8 microM and 0.9 microM, respectively. The emission spectra of the DnaJ-bound peptides suggests that DnaJ bound both D-peptides with the same main chain direction as L-peptides. Binding of the normal all-D and all-L peptides inhibited the DnaJ-induced stimulation of DnaK ATPase. However, binding of the retro all-D analog to DnaJ did not impair the stimulation, indicating the existence of separate binding sites for peptides and DnaK.
authors.affiliation: Biochemisches Institut der Universität Zürich, CH-8057 Zürich, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Feifel
authors.forename: H J
authors.initials: HJ
authors.lastname: Schönfeld
authors.forename: P
authors.initials: P
authors.lastname: Christen
mesh_terms: D015081:2-Naphthylamine / Q000031:analogs & derivatives; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D004789:Enzyme Activation; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D008024:Ligands; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism*; D013884:Thiosulfate Sulfurtransferase / Q000737:chemistry / Q000378:metabolism*
chemical_list: C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008024:Ligands; D018832:Molecular Chaperones; D010446:Peptide Fragments; C038518:acrylodan; D015081:2-Naphthylamine; D013884:Thiosulfate Sulfurtransferase; D000251:Adenosine Triphosphatases; C063842:dnaK protein, E coli