Folding stability of the kinetoplastid membrane protein-11 (KMP-11) from Leishmania infantum

Abstract

Kinetoplastid membrane protein-11 (KMP-11) is a major component of the cell surface of kinetoplastids, and acts as a potent B- and T-cell immunogen during Leishmania infection. Here we report that the Leishmania infantum KMP- 11 secondary structure adopts mainly an α-helical conformation at pH 7.5 and that its urea- and thermally-induced unfolding constitute a fully reversible two-step process. This allows estimation of a half-denaturation temperature of ≃65 °C, a ΔG(D)/(H2O) at 20 °C of ≃14.63 kJ · mol-1, and an increment of the reaction heat of ≃183.92 kJ · mol-1 and an entropy of ≃543.4 J · mol-1 · deg-1, respectively' for the native-denatured equilibrium of the KMP-11 in solution. We also report that the KPM-11 protein is induced to adopt a molten globule state at a pH range between pH 4 and pH 6. As a whole, the stability and the specific features of the denaturing effect induced by changes in pH are similar in KMP-11 to various other lipoproteins.