Incidence of partial charges on ion selectivity in potassium channels.
Potassium channels are membrane proteins known to select potassium over sodium ions at a high diffusion rate. We conducted ab initio calculations on a filter model of KcsA of about 300 atoms at the Hartree-Fock level of theory. Partial charges were derived from the quantum mechanically determined electrostatic potential either with Merz-Kollman or Hinsen-Roux schemes. Large polarization and/or charge transfer occur on potassium ions located in the filter, while the charges on sodium ions remain closer to unity. As a result, a weaker binding is obtained for K(+) ions. Using a simplified version of a permeation model based on the concerted-motion mechanism for ion translocation within the single-file ion channel [P. H. Nelson, J. Chem. Phys. 117, 11396 (2002)], we discuss how differences in polarization effects in the adducts with K(+) and Na(+) can play a role as for ionic selectivity and conductance.
Huetz
Philippe
P
Laboratoire de Physique Moléculaire, UMR CNRS 6624, Faculté des Sciences et Techniques, La Bouloie, Université de Franche-Comté, 25030 Besançon cedex, France. philippe.huetz@univ-fcomte.fr
Boiteux
Céline
C
Compoint
Mylène
M
Ramseyer
Christophe
C
Girardet
Claude
C
D003198:Computer Simulation; D004553:Electric Conductivity; D007477:Ions; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D011188:Potassium / Q000737:chemistry*; D015221:Potassium Channels / Q000737:chemistry* / Q000378:metabolism; D012964:Sodium / Q000737:chemistry*
D007477:Ions; D015221:Potassium Channels; D012964:Sodium; D011188:Potassium