Structural mapping of a chaperone-substrate interaction surface.

NMR spectroscopy is used to detect site-specific intermolecular short-range contacts in a membrane-protein-chaperone complex. This is achieved by an "orthogonal" isotope-labeling scheme that permits the unambiguous detection of intermolecular NOEs between the well-folded chaperone and the unfolded substrate ensemble. The residues involved in these contacts are part of the chaperone-substrate contact interface. The approach is demonstrated for the 70 kDa bacterial Skp-tOmpA complex.