Two-Dimensional 1H NMR Studies of Ca(II)-Binding Site in Proteins Using Paramagnetic Lanthanides(III) as Probes and Yb(III)-Substituted Bovine a-Lactalbumin as an Example

Li-June Ming
Department of Chemistry and Institute for Biomolecular Science
University of South Florida
Tampa, FL 33620

Substitution of Yb3+ for the Ca2+ in bovine a-lactalbumin affords a derivative that gives rise to several isotropically shifted H-1 NMR signals in the range 80 to –35 ppm in D2O. Despite the broadness of the isotropically shifted features, cross signals in both NOESY and COSY spectra have been detected. Several Asp residues in the metal-binding loop can be recognized in the 2D H-1 NMR spectra of this derivative, showing cross signals among the protons of a CbH2-CaH moiety. This paper reports 2D H-1 NMR studies of a paramagnetic lanthanide(III)substituted Ca2+-containing protein that may serve as a model for future NMR studies of other biochemically significant Ca2+ proteins.
(Read an introduction about paramagnetic Ln(III) ions as NMR probes)

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