ISOTOPE-FILTERED 2D NMR OF A PROTEIN PEPTIDE COMPLEX - STUDY OF A SKELETAL-MUSCLE MYOSIN LIGHT CHAIN KINASE FRAGMENT BOUND TO CALMODULIN

An NMR approach is demonstrated for elucidating the conformation of a peptide when tightly bound to a protein. A 26-residue peptide derived from rabbit skeletal muscle myosin light chain kinase, comprising the binding site for calmodulin, was complexed with uniformly (> 95%) N-15- and C-13-enriched calmodulin. Improved isotope-filtered two-dimensional NMR techniques were developed for suppressing NMR calmodulin signals. NOE patterns indicate that residues Arg-3 through Ser-21 of the bound peptide form an alpha-helix. NOE interactions between the peptide and the protein indicate that the N-terminal half of the peptide interacts with the C-terminal domain of calmodulin, and the C-terminal half interacts with the N-terminal calmodulin domain.