Beta-lactoglobulin structure and retinol binding changes in presence of anionic and neutral detergents.
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.
Taheri-Kafrani
Asghar
A
Laboratory of Biophysical Chemistry, Department of Chemistry, University of Isfahan, Isfahan, 81746-73441, Islamic Republic of Iran.
Bordbar
Abdol-Khalegh
AK
Mousavi
Seyed Habib-Allah
SH
Haertlé
Thomas
T
D000818:Animals; D001665:Binding Sites; D002151:Calorimetry; D002417:Cattle; D003902:Detergents / Q000494:pharmacology*; D007782:Lactoglobulins / Q000737:chemistry* / Q000378:metabolism*; D015394:Molecular Structure; D017830:Octoxynol / Q000494:pharmacology; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D014801:Vitamin A / Q000378:metabolism*
D003902:Detergents; D007782:Lactoglobulins; D014801:Vitamin A; D012967:Sodium Dodecyl Sulfate; D017830:Octoxynol