cis-Effect of DnaJ on DnaK in ternary complexes with chimeric DnaK/DnaJ-binding peptides

Chimeric peptides, comprising a DnaK-binding sequence of L-amino acid residues (motif k) and an exclusive DnaJ-binding sequence of D-amino acid residues (motif j) connected through a 22-residue linker, were examined as minisubstrates for the DnaK chaperone system. The DnaJ-stimulated ATPase activity of DnaK was three times higher in the presence of the chimeric peptides pjk or pkj than in the simultaneous presence of the corresponding single-motif peptides ala-p5 (k motif) Plus D-p5 (j motif). Apparently, pjk and pkj mimic unfolded proteins by forming ternary (ATP.DnaK)(.)peptide(.)DnaJ complexes which favor cis-interaction of DnaJ with DnaK. Con sistent with this interpretation, the specific stimulatory effect of the chimeric peptides was abolished by either single-motif peptide in excess. (C) 2004 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.