Motion in K channel [kchann]

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Classification Suspected Fragment Motion, Unclassifiable [F-?-1]

1k4c KcsA (closed)
1lnq MthK (open)

A somewhat similar type of motion to that in the nicotinic acetylcholine receptor has been proposed for the opening of the potassium channel. In a recent EPR spectroscopic study of its motion Perozo et. al. argue that this involves the rotation of a number of helices upon their axes and sidechains hopping between various interdigitating conformations -- somewhat similar to the concerted motions of enmeshed gears.
Site-directed mass tagging has been used to indirectly visualize the gating cycle (Kelly and Gross 2003), indicating a "significant conformational change" of the intracellular region.
More direct evidence for movement came from comparison of the KcsA channel and the open conformation of the MthK channel, which are structurally similar. In MthK, the inner helices are bent at a glycine residue which is also present in the analogous position in KcsA, and the movement of the helices leads to widening of the channel. The supplemental material on Nature's website accompanying Jiang et al. includes a movie of the opening and closing of the pore.

Jiang Y, Lee A, Chen J, Cadene M, Chait BT, MacKinnon R (2002). The open pore conformation of potassium channels. Nature 417:523-6. [Medline info for 12037560]
Perozo E, Cortes DM, Cuello LG (1999). Structural rearrangements underlying K+-channel activation gating. Science 285:73-8. [Medline info for 10390363]
Zhou Y, Morais-Cabral JH, Kaufman A, MacKinnon R (2001). Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 A resolution. Nature 414:43-8. [Medline info for 11689936]
Sonnleitner A, Mannuzzu LM, Terakawa S, Isacoff EY. Structural rearrangements in single ion channels detected optically in living cells. Proc Natl Acad Sci U S A. 2002 Oct 1;99(20):12759-64. [Medline info for 12228726]
Kelly BL, Gross A (2003). Potassium channel gating observed with site-directed mass tagging. Nat Struct Biol. 10:280-4. [Medline info for 12640442]

GO terms associated with structures
Molecular functionpotassium channel activity, cation transporter activity
Cellular componentmembrane
Biological processpotassium ion transport

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Copyright 1995-2005 M. Gerstein, W. Krebs, S. Flores, N. Echols, and others
Email: Mark.Gerstein _at_