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Crystal structure of the eukaryotic strong inward-rectifier K+ channel Kir2.2 (3JYC)

Crystal structure of the eukaryotic strong inward-rectifier K+ channel Kir2.2 (3JYC). A Potassium-Gated Ion Channel in Chickens (at 3.1 Angstrom resolution) By: Afif Hossain. Assumed Biological Assembly. Inward Rectifiers.

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Crystal structure of the eukaryotic strong inward-rectifier K+ channel Kir2.2 (3JYC)

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  1. Crystal structure of the eukaryotic strong inward-rectifier K+ channel Kir2.2 (3JYC) A Potassium-Gated Ion Channel in Chickens (at 3.1 Angstrom resolution) By: AfifHossain

  2. Assumed Biological Assembly

  3. Inward Rectifiers • Ion-conduction property where the degree of one-way conduction is great or small • For 3JYC, K+ conductance into the cell is much greater than its conductance out of the cell (given a charge gradient) • Interestingly, the Kir channels are similar to one-way conductors, or mechanically speaking, like the diodes that make up electronic devices. • Inward rectification is caused by cations like Mg2+. • During internal negative membrane voltages (hyperpolarization), K + ions can freely be conducted. • However, when internal membrane voltages are positive (depolarization), conduction of K + ions is blocked. • Thus, Kir channels conduct K + ions in excitable cells only when at rest; they are nonconductive in excited cells. • Experimentally, this exhibits energy efficiency because the Kir channels not only can regulate the resting membrane potential of cells, but also maintain a K + gradient during an action potential

  4. Asymetrical Unit

  5. 3JYC Structure, Binding Sites Highlighted Binding sites along the ion conduction pathway that are both conductive and inhibitory: rubidium (Rb +), strontium (Sr 2+), and europium (Eu3+) ions that facilitate conduction/inhibition

  6. 3JYC Structure, Colored Residues

  7. 3JYC Structure, Atoms Transparent and Space-Filling

  8. Interesting Facts About 3JYC • Kir channels are relatively unaffected by natural toxins that normally inhibit other K + channels • For example, snake, spider, and scorpion venoms contain toxins against certain Kv channels, (or potassium voltage-dependent channels • On the other hand, very few Kir channel specific toxins are known • The Kir2.2 channel from chicken is 90% identical to the humanortholog and its sequences exhibit all of the characteristics that would make it an inward rectifier. • Diffraction crystals are obtained by intrinsicallydisordering N- and C-terminal regions (transparency) • Heritable mutations cause periodic paralysis and cardiac arrhythmia

  9. 3JYC Structure, Sans Nitrogen and Carbon

  10. A, Ala- red C, Cys- blue D, Asp- green E, Glu- purple F, Phe- cyan G, Gly- magenta H, His- yellow I, Ile- dim gray K, Lys- orange L, Leu- hot pink M, Met- forest green N, Asn- light sea green P, Pro- cornflower blue Q, Gln- orange red R, Arg- white S, Ser-light gray T, Thr- gray V, Val- dark gray W, Trp- medium blue Y, Tyr- black Amino Acid Structure of 3JYC by Color

  11. Bibliography • http://www.sciencemag.org/cgi/content/full/326/5960/1668#F1 • http://www.rcsb.org/pdb/explore/explore.do?structureId=3JYC • http://www.elp.manchester.ac.uk/pub_projects/2002/MNQJ9PP2/Webpages/kv_channels.htm

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