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Effects of pH and protein conformation on in-solution complexation between bovine alpha-lactalbumin and oleic acid: Binding trend analysis by using SPR and ITC

Title
Effects of pH and protein conformation on in-solution complexation between bovine alpha-lactalbumin and oleic acid: Binding trend analysis by using SPR and ITC
Author
이은규
Keywords
Protein-fatty acid complex; alpha-Lactalbumin; Oleic acid; Binding affinity; HAMLET; SPR; ITC; Molecular interactions
Issue Date
2015-10
Publisher
ELSEVIER SCI LTD
Citation
PROCESS BIOCHEMISTRY, v. 50, NO 9, Page. 1379-1387
Abstract
To analyze the trends in molecular interaction between bovine alpha-LA (BLA) and oleic acid, we investigated the effects of pH and protein conformation on oleate binding to BLA and compared the order-ofmagnitude differences in binding behavior. Both isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) were used. For the ITC experiments, a solution of holo- or apo-BLA was titrated with sodium oleate at pH 4.0 and 10.0 to look for protein surface charge effects. In the SPR experiments, BLA was immobilized on the chip surface and sodium oleate solutions at various pHs (4.0, 5.5, 7.0,8.5 and 10.0) were injected. Binding stoichiometry of ca. 5.2 molecules of oleate per unit molecule of BLA was observed. apo-BLA at a lower pH (lower than the pl of alpha-LA) yielded stronger binding avidity and affinity, which indicated that electrostatic interactions between the basic residues and the negatively charged carboxyl groups may play a major role in the complexation, in addition to hydrophobic interactions. The complexes formed at pH 4.0 and 5.5 were relatively unstable and rapidly dissociated when exposed to pH 7.0. In summary, we propose that the complexation can be regarded as a very weak (or, transient) and multivalent binding, requiring both electrostatic and hydrophobic interactions, probably in series and also in a dynamic equilibrium. (C) 2015 Elsevier Ltd. All rights reserved.
URI
http://www.ijsp-online.com/content/abstracts/abstract4502.php#c02
ISSN
1359-5113; 1873-3298
DOI
10.1016/j.procbio.2015.05.018
Appears in Collections:
GRADUATE SCHOOL[S](대학원) > BIONANOTECHNOLOGY(바이오나노학과) > Articles
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