User:Amy Kerzmann/Sandbox 3
From Proteopedia
Voltage-gated Potassium Channel
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| 1bl8, resolution 3.20Å () | |||||||||
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| Resources: | FirstGlance, OCA, RCSB, PDBsum | ||||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||||
Backgound
This crystal structure illuminated the principles of ion selectivity when it was solved in 1998.[1] To further demonstrate the importance of this structure, the 2003 Nobel Prize in Chemistry was awarded to the principal investigator, Roderick MacKinnon.
Channel Structure:
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As described by Doyle, et al in their original paper, the potassium channel forms an "inverted teepee, or cone" with the widest portion facing the extracellular space.[1] Almost the entire structure is buried within the lipid bilayer, which is evident when the structure is colored according to the of each sidechain (hydrophobic residues are shown in grey and hydrophilic in purple.)
As indicated by the coloring of the , this channel is a homotetramer, which means that it is comprised of four identical protein chains or . Each monomer is predominantly alpha , with no beta strands. When viewed in (where the N-terminus is blue and the C-terminus is red), one can see that both termini are located on the cytosolic side of the membrane. The central core of the potassium channel is comprised of the two C-terminal helices from each monomeric subunit. The region between these two helices will be our main focus, as it lines the cavity and makes contacts with the migrating potassium ions.
The central core of this protein is comprised of eight helices, two from each monomeric subunit. Since each has the same orientation in the membrane, the protein has a four-fold rotational symmetry when viewed from the membrane surface. As a result, each of the channel-lining residues appears as a ring of four identical sidechains. This principle is represented by the conserved residues that function as selectivity filters within the cavity. Additional and residues line the channel. Looking at a of these residues, one can see that some hydrophobic patches remain within the cavity.
Channel Function:
Here's how it works.
References
