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Bovine beta-lactoglobulin: interaction studies with palmitic acid
L Ragona1, F Fogolari, L Zetta
1Laboratorio NMR, ICM, Milano, Italy.
Protein Science : a Publication of the Protein Society
|August 10, 2000
Summary
Bovine beta-lactoglobulin binds palmitic acid in its central cavity. This interaction is reversible and pH-dependent, suggesting a role in milk fat digestion for calves.
Area of Science:
- Biochemistry
- Structural Biology
- Dairy Science
Background:
- Bovine beta-lactoglobulin (BLG) is known to complex with fatty acids in vivo.
- The precise structure-function relationship of BLG-fatty acid interactions remains unclear.
- Understanding these interactions is crucial for dairy science and nutrition.
Purpose of the Study:
- To investigate the structure-function relationship of bovine beta-lactoglobulin (BLG) and its interaction with palmitic acid (PA).
- To elucidate the binding site and conformational changes of BLG upon PA binding across a wide pH range.
- To assess the pH-dependent release and reversibility of PA from BLG.
Main Methods:
- Utilized 13C-enriched palmitic acid (PA) for interaction studies.
- Employed one-, two-, and three-dimensional Nuclear Magnetic Resonance (NMR) spectroscopy.
- Investigated the pH range from 8.4 down to 2.1.
Main Results:
- Palmitic acid binds within the central cavity of BLG at neutral pH, with the methyl end deeply buried.
- Conformational variability of the bound PA carboxyl end was observed between pH 8.4 and 5.9, linked to the Tanford transition.
- PA release initiates below pH 6.0 and is nearly complete at acidic pH, with reversible binding across the entire pH range.
Conclusions:
- BLG exhibits pH-dependent binding and release of palmitic acid, crucial for its proposed role as a fatty acid transporter.
- The reversible nature of BLG-PA interaction differs from other fatty acid-binding proteins.
- These findings support the hypothesis that BLG facilitates milk fat digestion in neonatal calves.