Atypical mechanism of conduction in potassium channels.
Potassium channels can conduct passively K+ ions with rates of up to approximately 10(8) ions per second at physiological conditions, and they are selective to these species by a factor of 10(4) over Na+ ions. Ion conduction has been proposed to involve transitions between 2 main states, with 2 or 3 K+ ions occupying the selectivity filter separated by an intervening water molecule. The largest free energy barrier of such a process was reported to be of the order of 2-3 kcal mol(-1). Here, we present an alternative mechanism for conduction of K+ in potassium channels where site vacancies are involved, and we propose that coexistence of several ion permeation mechanisms is energetically possible. Conduction can be described as a more anarchic phenomenon than previously characterized by the concerted translocations of K+-water-K+.
Furini
Simone
S
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX13QZ, United Kingdom.
Domene
Carmen
C
D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology; D001665:Binding Sites; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D015640:Ion Channel Gating; D008958:Models, Molecular; D011188:Potassium / Q000737:chemistry; D015221:Potassium Channels / Q000737:chemistry* / Q000502:physiology; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D001426:Bacterial Proteins; D015221:Potassium Channels; C107790:prokaryotic potassium channel; D014867:Water; D011188:Potassium