13C nuclear magnetic resonance study of molecular motions and conformational transitions in muscle calcium binding parvalbumins.

13C nuclear magnetic resonance is used to detect the Ca2+ ion controlled conformational transition in muscle calcium binding parvalbumin and to study its intramolecular motions. Nuclear relaxation parameters are used to evaluate the reorientation rates of the protein and some of the amino acid side chains. While peripheral residues exhibit greater motional freedom than the protein interior, an interesting finding is that significant rapid internal motion is present in the phenylalanine rings comprising the hydrophobic core of the protein.