User:Lori Wetmore/Sandbox 2

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Look for a family of channels (ion or otherwise) or transporters.

I'm going to discuss the family of potassium ion channels, and the specific channel I'll be using to illustrate will be the KcsA potassium ion channel. (http://www.rcsb.org/pdb/explore/explore.do?structureId=1k4c) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2383984/ http://www.ks.uiuc.edu/Research/smd_imd/kcsa/ http://jgp.rupress.org/content/128/5/569.long http://www.ncbi.nlm.nih.gov/pubmed/18621821 http://ion.ucdavis.edu/pdfs/bj02-KcsA.pdf http://ion.ucdavis.edu/pdfs/kchan1.pdf http://www.ncbi.nlm.nih.gov/Structure/mmdb/mmdbsrv.cgi?uid=12521


Here are just a few of the things that I'll want to incorporate into my page at some point:

When viewed in (where the N-terminus is gradually shaded into the C-terminus according to the scale below)

N               C

The structure of the KcsA K+ channel

Drag the structure with the mouse to rotate

Contents

KcsA: A K+ channel

Potassium, a major cation in most cells, is responsible (in addition to other cations such as sodium) for the creation of the cell membrane potential, which is responsible for the generation of an action potential, which is necessary for a number of cellular functions such as neurotransmission, muscle contraction, and heart function. The proper balance of potassium in the cell is maintained by potassium ion pumps in the cellular membrane. To date, there are five potassium ion channels with a resolved structure (KcsA, KirBac1.1, KirBac3.1, KvAP, MthK), with KirBac3.1 being the most recently resolved, and they are all tetramers with several conserved secondary structural elements. [1]


Channel Structure

As previously mentioned, potassium channels have a tetrameric structure in which four identical protein subunits associate to form a homotetramer, or a fourfold symmetric complex arranged around a central ion conducting pore. Alternatively four related but not identical protein subunits may associate to form heterotetrameric complexes with pseudo C4 symmetry. All potassium channel subunits have a distinctive pore-loop structure that lines the top of the pore and is responsible for potassium selective permeability. There are over 80 mammalian genes that encode potassium channel subunits. However potassium channels found in bacteria are amongst the most studied of ion channels, in terms of their molecular structure. Using X-ray crystallography, [2] [3] profound insights have been gained into how potassium ions pass through these channels and why sodium ions, which are much smaller than potassium ions, do not. [4]

Selecvitity Filter/s

Channel Function

Gating Mechanism

Ongoing Research

References

  1. ↑ Hellgren M, Sandberg L, Edholm O. A comparison between two prokaryotic potassium channels (KirBac1.1 and KcsA) in a molecular dynamics (MD) simulation study. Biophys Chem. 2006 Mar 1;120(1):1-9. Epub 2005 Oct 25. PMID:16253415 doi:10.1016/j.bpc.2005.10.002
  2. ↑ Doyle DA, Morais Cabral J, Pfuetzner RA, Kuo A, Gulbis JM, Cohen SL, Chait BT, MacKinnon R. The structure of the potassium channel: molecular basis of K+ conduction and selectivity. Science. 1998 Apr 3;280(5360):69-77. PMID:9525859
  3. ↑ MacKinnon R, Cohen SL, Kuo A, Lee A, Chait BT. Structural conservation in prokaryotic and eukaryotic potassium channels. Science. 1998 Apr 3;280(5360):106-9. PMID:9525854
  4. ↑ Armstrong C. The vision of the pore. Science. 1998 Apr 3;280(5360):56-7. PMID:9556453


[1]

Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 A resolution.Zhou, Y., Morais-Cabral, J.H., Kaufman, A., MacKinnon, R. Journal: (2001) Nature 414: 43-48 PubMed: 11689936 View PubMed Abstract at NCBI DOI: 10.1038/35102009

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Lori Wetmore

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