Principal component analysis of the pH-dependent conformational transitions of bovine β-lactoglobulin monitored by heteronuclear NMR
- 25 September 2007
- journal article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 104 (39), 15346-15351
- https://doi.org/10.1073/pnas.0702112104
Abstract
To clarify the pH-dependent conformational transitions of proteins, we propose an approach in which structural changes monitored by heteronuclear sequential quantum correlation (HSQC) spectroscopy were analyzed by using a principal component analysis (PCA). We use bovine beta-lactoglobulin, a protein widely used in protein folding studies, as a target. First, we measured HSQC spectra at various pH values and subjected them to a PCA. The analysis revealed three apparent transitions with pK(a) values of 2.9, 4.9, and 6.8, consistent with previous reports using different methods. Next, Gdn-HCl-induced unfolding was examined by measuring tryptophan fluorescence at various pH values. Between pH 2 and 8, beta-lactoglobulin exhibited a number of structural transitions as well as changes in stability represented by the free energy change of unfolding, DeltaG(U). By combining the NMR and fluorescence results, the change in DeltaG(U) was suggested to result from the decreased pK(a) of some acidic residues. Notably, the native state at neutral pH is destabilized by deprotonation of Glu-89, leading to an increase in the relative population of the intermediate. Thus, the PCA of pH-dependent HSQC spectra provides a more comprehensive understanding of the stability and function of proteins.Keywords
This publication has 31 references indexed in Scilit:
- Dynamics and Mechanism of the Tanford Transition of Bovine β-Lactoglobulin Studied using Heteronuclear NMR SpectroscopyJournal of Molecular Biology, 2006
- Multivariate Curve Resolution Applied to the Analysis and Resolution of Two-Dimensional [1H,15N] NMR Reaction SpectraAnalytical Chemistry, 2004
- Protein self‐association in solution: The bovine β ‐lactoglobulin dimer and octamerProtein Science, 2003
- Characterization of pH-induced transitions of β-lactoglobulin: ultrasonic, densimetric, and spectroscopic studiesJournal of Molecular Biology, 2001
- The core lipocalin, bovine β-lactoglobulinBiochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 2000
- Rapid collapse and slow structural reorganisation during the refolding of bovine α-lactalbuminJournal of Molecular Biology, 1999
- Monomeric bovine β‐lactoglobulin adopts a β‐barrel fold at pH 2FEBS Letters, 1998
- Structural and conformational changes of β-lactoglobulin B: an infrared spectroscopic study of the effect of pH and temperatureBiochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1988
- Proton relaxation rates of water in dilute solutions of β-lactoglobulin. Determination of cross relaxation and correlation with structural changes by the use of two genetic variants of a self-associating globular proteinBiochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1985
- The Reversible Transformation of β-Lactoglobulin at pH 7.51Journal of the American Chemical Society, 1959