Biophysical characterization of interaction between apolipoprotein A-I and bacterial lipopolysaccharide

HENNING M F; GARDA H A; BAKÁS L S

CELL BIOCHEMISTRY AND BIOPHYSICS

Humana Press

Año: 2006 vol. 44 p. 490 - 496

1085-9195

We studied the effect of bacterial lipopolysaccharide-apolipoprotein A-I interaction on the structure and function of this protein. The micellization process of dimirystoil phosphatidylcholine liposomes (MLV-DMPC) by apo A-I in the presence of LPS was characterized. Apo A-I may interact with MLV-DMPC at 24.5ºC forming micellar complexes at 2.5:1 lipid: protein ratio (w/w). The kinetics of MLV micellization was studied by turbidity of DMPC suspensions. In the presence of LPS, micellization takes place at the same initial rate, but the extension decreases at 62 % and 37 % when the protein was incubated previously with LPS at 1:0.1 or 1:1 apo A-I: LPS ratio after 90 min, respectively. The micellization products contain 3 apo A-I molecules per particle at 1:01 protein:LPS ratio (as in the absence of LPS) but at 1:1 ratio, the particles only contains 2 apo A-I molecules. On the other hand, a decrease of intrinsic fluorescence intensity of the protein was observed in the presence of increasing LPS concentration. Finally, we studied the effect of LPS on the Tt of MLV-DMPC without detecting changes in Tt.  In conclusion, the changes found in the micellization process are mainly due to changes in the Apo AI conformation by LPS interaction in solution.