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Human alpha-lactalbumin (alpha-LA), a 123-residue calcium-binding protein, has been studied using (15)N NMR relaxation methods in order to characterize backbone dynamics of the native state at the level of individual residues. Relaxation data were collected at three magnetic field strengths and analyzed using the model-free formalism of Lipari and Szabo. The order parameters derived from this analysis are generally high, indicating a rigid backbone. A total of 46 residues required an exchange contribution to T(2); 43 of these residues are located in the alpha-domain of the protein. The largest exchange contributions are observed in the A-, B-, D-, and C-terminal 3(10)-helices of the alpha-domain; these residues have been shown previously to form a highly stable core in the alpha-LA molten globule. The observed exchange broadening, along with previous hydrogen/deuterium amide exchange data, suggests that this part of the alpha-domain may undergo a local structural transition between the well-ordered native structure and a less-ordered molten-globule-like structure.

Original publication

DOI

10.1021/bi900023m

Type

Journal article

Journal

Biochemistry

Publication Date

19/05/2009

Volume

48

Pages

4031 - 4039

Keywords

Amino Acid Sequence, Cysteine, Disulfides, Humans, Hydrogen-Ion Concentration, Lactalbumin, Models, Molecular, Molecular Sequence Data, Nuclear Magnetic Resonance, Biomolecular, Protein Structure, Secondary, Protein Structure, Tertiary, Recombinant Proteins, Sequence Homology, Amino Acid, Temperature