Effect of the secondary structure of carbohydrate residues of alpha 1-acid glycoprotein (orosomucoid) on the local dynamics of Trp residues.
We studied in this work the relation between the secondary structure of the carbohydrate residues of alpha1-acid glycoprotein and the local motions of Trp residues of the protein. We measured for this purpose the fluorescence emission intensity and anisotropy of the Trp residues between -46 and +30 degrees of the sialylated and asialylated protein. Our results indicate that, in both forms, the global profile of the emission intensity with temperature shows that Trp residues display static and collisional interaction with the neighboring amino acids. However, the profile of the asialylated form is more structured than that observed for the sialylated protein. The Y-plot analysis of the emission-anisotropy results indicated that the frictional resistance to rotation of the surface Trp residue is less important in the sialylated protein than in the asialylated form. This result is in good agreement with the fact that, in the asialylated conformation, the carbohydrate residues are closer to the protein surface than in the sialylated form, thereby increasing the contact of the surface Trp residue with the neighboring amino acids. Also, the interaction between the carbohydrate residues and the surface Trp residue contributes to the modification of the frictional resistance to rotation of the fluorophore.
Albani
Jihad René
JR
Laboratoire de Biophysique Moléculaire, Université des Sciences et Technologies de Lille, Bâtiment C6, F-59655 Villeneuve d'Ascq. Jihad-Rene.Albani@univ-lille1.fr
D002241:Carbohydrates / Q000737:chemistry; D009961:Orosomucoid / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry*
D002241:Carbohydrates; D009961:Orosomucoid; D014364:Tryptophan