The influences of protonation state of histidine on aromatic/arginine region of aquaporin-1 protein

Abstract

Aquaporin-1 (AQP1) is widely distributed in the epithelial tissue for water absorption and secretion. The histidine (His182) residue in the aromatic/arginine (ar/R) constriction region plays an important role in transporting water through the membrane. In this study, we have performed a total of 46 ns equilibrium molecular dynamics (MD) simulations, and obtained the influence of His182 in two protonation states (Hsd is the proton at Nδ and Hse is the proton at Nϵ) on the ar/R region. Water permeation rate shows that it is easier for water molecules to permeate the ar/R region of the AQP1 with residue in the Hsd state than in the Hse state. The minimum radii of the pore in the ar/R region were calculated during the last 10 ns MD simulation. We have analysed the correlation among the state of the pore (open or close), the minimum radius of the ar/R region and the dihedral angles < Cβ-Cγ-Cδ-Nϵ of Arg197. The results show that the minimum radius can be used to mark the state of the pore.