Abstract
This chapter discusses the results of NMR studies of five calmodulin (CaM)-binding peptides aimed at determining the existence and the nature of peptide-induced conformational changes in CaM. Titrations were performed at a CaM concentration of 0.5 mM in the NMR tube. In their original characterization of M13 as a CaM-binding domain, Blumenthal et al. noted that the peptide sequence exhibited α-helical probability >1 for residues 1–18. The results indicate that a single high-affinity species of peptide-CaM complex is formed and that the conformation of both the peptide and CaM are markedly altered upon complex formation, thus supporting our earlier conclusions based on the 27-residue peptide M13. The NMR results obtained for the CaM-binding peptides are more complex. The demonstration that different peptides induce different conformational changes in CaM provides the first structural evidence for a model for CaM-target enzyme interactions in which an enzyme-specific conformational change in CaM plays an important role in the enzyme's activation.
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