Effect of 1-Aminoanthracene (1-AMA) Binding on the Structure of Three Lipocalin Proteins, the Dimeric β Lactoglobulin, the Dimeric Odorant Binding Protein and the Monomeric α1-Acid Glycoprotein. Fluorescence Spectra and Lifetimes Studies

Abstract

We studied effect of 1-aminoanthracene (1-AMA) binding on the structures of dimeric β lactoglobulin, dimeric odorant binding protein (OBP) and monomeric α(1)-acid glycoprotein (lipocalin family proteins) by monitoring fluorescence excitation spectra and measuring fluorescence lifetimes of the tryptophan residues of the proteins. Results show that binding of 1-AMA to β lactoglobulin and OBP modifies their conformation even at low probe concentration compared to that of the proteins. Structural modification induces a red shift of the fluorescence excitation spectra maximum of tryptophan residues accompanied with an increase of the third fluorescence lifetime and a decrease of its pre-exponential factor. These effects were not observed for α(1)-acid glycoprotein, probably as the result of carbohydrate presence. These data raise doubts concerning use of 1-AMA as a probe to study biological properties of β lactoglobulin and OBP.