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A homology model has been generated for the pore-forming domain of Kir6.2, a component of an ATP-sensitive K channel, based on the x-ray structure of the bacterial channel KcsA. Analysis of the lipid-exposed and pore-lining surfaces of the model reveals them to be compatible with the known features of membrane proteins and Kir channels, respectively. The Kir6.2 homology model was used as the starting point for nanosecond-duration molecular dynamics simulations in a solvated phospholipid bilayer. The overall drift from the model structure was comparable to that seen for KcsA in previous similar simulations. Preliminary analysis of the interactions of the Kir6.2 channel model with K(+) ions and water molecules during these simulations suggests that concerted single-file motion of K(+) ions and water through the selectivity filter occurs. This is similar to such motion observed in simulations of KcsA. This suggests that a single-filing mechanism is conserved between different K channel structures and may be robust to changes in simulation details. Comparison of Kir6.2 and KcsA suggests some degree of flexibility in the filter, thus complicating models of ion selectivity based upon a rigid filter.

Original publication

DOI

10.1016/S0006-3495(00)76833-0

Type

Journal article

Journal

Biophys J

Publication Date

06/2000

Volume

78

Pages

2929 - 2942

Keywords

Amino Acid Sequence, Bacterial Proteins, Computer Graphics, Computer Simulation, Humans, Models, Molecular, Molecular Sequence Data, Potassium Channels, Potassium Channels, Inwardly Rectifying, Protein Conformation, Protein Folding, Protein Structure, Secondary, Sequence Alignment, Sequence Homology, Amino Acid