The native conformation of plasmepsin II is kinetically trapped at neutral pH

作者：Xiao Huogen; Dee Derek; Yada Rickey Y^*

来源：Archives of Biochemistry and Biophysics, 2011, 513(2): 102-109.

DOI：10.1016/j.abb.2011.06.017

• Plasmepsin II
• Aspartic protease
• Folding
• Prosegment
• Zymogen
• Stability
• Kinetics

Plasmepsin II (PMII), an aspartic protease from the malarial parasite Plasmodium falciparum, represents a model for understanding protease structure/function relationships due to its unique structure and properties. The present study undertook a thermodynamic and kinetic analysis of the PMII folding mechanism and a pH stability profile. Differential scanning calorimetry revealed that the native state of PMII (Np) was irreversibly unfolded, and in the pH range of 6.5-8.0, PMII refolds to a denatured state (Rp) with higher thermal stability than Np. Rp could also be formed upon partially unfolding PMII at pH 11.0 and 37 degrees C for 2 h, followed by adjustment to a pH in the range of 6.5-8.0. While Rp could be folded/unfolded reversibly, Np was shown to exist as a kinetically trapped state. By examining the unfolding kinetics of Np and the kinetics of Rp folding to Np at 25 degrees C, it was found that Np is kinetically trapped by an unfolding barrier of 25.5 kcal/mol, and yet once unfolded, is prevented from folding by a comparable folding barrier. The folding mechanism of PMII is similar to that reported for pepsin. It is hypothesized that the PMII zymogen also utilizes a prosegment-catalyzed folding mechanism.

• 出版日期2011-9-15