A mechanism for ion selectivity in potassium channels: computational studies of cation-pi interactions.
A combination of computational methods has been used to evaluate the interaction between the pi face of a benzene molecule and the monovalent cations of lithium, sodium, potassium, and rubidium. In the gas phase, the ions are strongly bound, and the affinity for benzene follows the expected electrostatic trend (lithium, largest; rubidium, smallest). However, in an aqueous environment, a reordering occurs such that the potassium ion is preferred over all the other ions for 2:1 benzene:ion complexes. The selectivity sequence parallels that seen in voltage-gated potassium channels. Given that several conserved aromatic residues are present in the pore region of such channels, these results suggest that the cation-pi interaction may be responsible for the ion selectivity in potassium channels.
Kumpf
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Arnold and Mabel Beckman Laboratories of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125.
Dougherty
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D000595:Amino Acid Sequence; D001554:Benzene / Q000737:chemistry / Q000378:metabolism*; D002412:Cations / Q000737:chemistry / Q000378:metabolism*; D008094:Lithium / Q000737:chemistry / Q000378:metabolism; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009010:Monte Carlo Method; D011188:Potassium / Q000737:chemistry / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism*; D012413:Rubidium / Q000737:chemistry / Q000378:metabolism; D012964:Sodium / Q000737:chemistry / Q000378:metabolism; D013816:Thermodynamics
D002412:Cations; D015221:Potassium Channels; D008094:Lithium; D012964:Sodium; D001554:Benzene; D012413:Rubidium; D011188:Potassium