BINDING OF AN N-TERMINAL RHODANESE PEPTIDE TO DNAJ AND TO RIBOSOMES

A peptide corresponding to the N-terminal 17 amino acids of bovine rho danese was fluorescently labeled with a coumarin derivative at its pri mary amino group(s) and then purified by high performance liquid chrom atography. This peptide interacted with the molecular chaperone DnaJ i n the absence of other chaperones and ATP, In the presence of ATP, the molecular chaperone DnaK bound to the DnaJ-peptide complex, but not t o the peptide alone, The chaperone GrpE appeared to cause the release of the peptide bound to the ternary complex in the presence of ATP but not in the presence of ADP, This nucleotide apparently stabilized the complex, The peptide also bound to salt-washed Escherichia coli 70 S ribosomes, specifically to 50 S ribosomal subunits, not to 30 S subuni ts, DnaJ plus DnaK interacted with the peptide on the ribosome, GrpE c aused dissociation of the peptide from the ribosome; ATP was required for this reaction, It was inhibited by ADP, A comparable series of cha perone-mediated reactions is assumed to occur with the N-terminal segm ent of the nascent polypeptide to facilitate its folding on ribosomes.