β-Lactoglobulin Structure and Retinol Binding Changes in Presence of Anionic and Neutral Detergents

Abstract

Bovine beta-lactoglobulin (beta-LG) in vivo (in milks) has been found in complexes with lipids such as butyric and oleic acids. To elucidate the still unknown structure-function relationship in this protein, the structural changes of beta-lactoglobulin variant A (beta-LG A) in the presence of anionic surfactant such as sodium n-dodecyl sulfate (SDS) and in the presence of nonionic surfactant such as Triton X-100 have been investigated. Subsequently, the retinol binding by beta-LG has been investigated in the presence of various amounts of these surfactants as its binding indicator. The results of UV-vis and fluorescence studies show a higher denaturating effect of SDS at acid pH that can be due to greater positive charges of beta-LG at this pH indicating also the nonspecific hydrophobic interactions of Triton X-100 with beta-LG at all studied pHs. Isothermal titration calorimetry (ITC) measurements indicate the endothermic nature of beta-LG/SDS interactions and the exothermic nature of Triton X-100/beta-LG interactions. The analysis of the binding data demonstrates the absence of considerable changes in retinol binding properties of beta-LG in the presence of various amounts of these surfactants. This implies that surfactant binding does not change the conformation of beta-LG in the regions defining the retinol-binding site.

Production, characterization and foamability of α-lactalbumin/glycomacropeptide supramolecular structures

“…In addition, an increase in peak emission intensity was observed. These findings indicate that the surrounding chemical environment of the chromophores became more apolar (Jindal & Naeem, 2013;Taheri-Kafrani, Asgari-Mobarakeh, Bordba, & Haertlé, 2010;Taheri-Kafrani, Bordbar, Mousavi, & Haertlé, 2008;Zhang, Qi, Zheng, Li, & Liu, 2009), suggesting that during the interaction between α-la and GMP molecules, the chromophores remain buried deeper in the core structures composed of these molecules ( Fig. 4a and b).…”

Binding of streptomycin with bovine serum albumin: Energetics and conformational aspects

“…Though the interactions of some antibiotics with the serum albumin are reported in literature [11,[17][18][19], quantitative studies on the interaction of streptomycin with serum albumin addressing the energetics and type of interactions is not available in literature. A combination of isothermal titration calorimetry and fluorescence spectroscopy has yielded valuable information on binding interactions in biologically important systems both quantitatively and qualitatively [20][21][22][23][24][25]. In this work, we have used isothermal titration calorimetry in determining binding affinity, enthalpy, entropy and stoichometry …”

Fluorescence spectroscopic study on interaction of retinol with β-lactoglobulin in the presence of cetylpyridinium chloride

“…BLG may play important roles in the binding and transporting hydrophobic ligands such as retinoids, alkenes and fatty acids. Different methods have been used for investigating its interactions with amphiphilic and hydrophobic ligands such as retinoids, long chain fatty acids and surfactants [26,27]. This small globular protein has a three-dimensional structure consisting of one α-helix and nine anti-parallel β-strands with eight β-sheets folded into a cone-shaped barrel forming a hydrophobic pocket [25].…”

“…Several studies on the retinol binding of BLG in the presence of various surfactants have been done, recently [23,24,26,27]. BLG has conformational changes during its interaction with sodium n-dodecyl sulfate (SDS) and Triton X-100 while retinol binding properties of BLG do not show significant changes in the presence of these surfactants [27].…”

“…BLG has conformational changes during its interaction with sodium n-dodecyl sulfate (SDS) and Triton X-100 while retinol binding properties of BLG do not show significant changes in the presence of these surfactants [27]. Moreover, the retinol binding affinity has been measured in the presence of cationic n-decyltrimethyl ammonium bromides (C n TABs).…”