Peptide-binding specificity of the molecular chaperone BiP.

Members of the heat-shock protein family (hsp70s) can distinguish folded from unfolded proteins. This property is crucial to the role of hsp70s as molecular chaperones and is attributable to the amino-acid specificity of the peptide-binding site. The specificity for peptide ligands is investigated using a set of peptides of random sequence but defined chain length. The peptide-binding site selects for aliphatic residues and accommodates them in an environment energetically equivalent to the interior of a folded protein.