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

Kinetoplastid membrane protein-11 (KMP-11) is a major component of the cell surface of kinetoplastids, and acts as a potent B- and T-celI immunogen du ring Leishmania infection. Here we report that the Leishmania infantum KMP- 11 secondary structure adopts mainly an a-helical conformation at pH 7.5 an d that its urea- and thermally-induced unfolding constitute a fully reversi ble two-step process. This allows estimation of a half-denaturation tempera ture of approximate to 65 degrees C, a Delta G(D)(H2O) at 20 degrees C of a pproximate to 14.63 kJ.mol(-1), and an increment of the reaction heat of ap proximate to 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 soluti on. We also report that the KPM-11 protein is induced to adopt a molten glo bule state at a pH range between pH 4 and pH 6. As a whole, the stability a nd the specific features of the denaturing effect induced by changes in pH are similar in KMP-11 to various other lipoproteins.