| 초록 |
Aquaporins are transmembrane channels found in cell membranes of all life forms. We examine their apparently paradoxical property, facilitation of efficient permeation of water while excluding protons and ions. Potential of Mean Force is calculated with Molecular Dynamics(MD) simulation to investigate the free energy profile of water molecules passing through the channel. It is found that two conserved asparagines force a central water molecule to serve strictly as a hydrogen bond donor to its neighboring water molecules. Assisted by the electrostatic potential generated by two half membrane spanning loops, this dictate opposite orientations of water molecules in the two halves of the channel, and thus prevents the formation of a “proton wire”, while permitting rapid water diffusion. Also, ion exclusion mechanism is studied with the same method. |
