1H NMR studies of mastoparan binding by calmodulin

Association with the cytoactive tetradecapeptide mastoparan perturbs the downfield 1H NMR spectrum of the calmodulin-Ca42+ complex. Changes occur in the resonances assigned to His-107 and Tyr-138. Composite peaks assigned to Phe-16 and Phe-89 and to Phe-68 and Tyr-99 are also affected. Both the upfield and downfield 1H NMR spectra contain evidence for spectroscopically distinct intermediates in Ca2+ binding by the calmodulin-mastoparan complex.