Lectures 12 - 14 - Membranes

• helps stabilize protein in membrane k ion channel

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Unformatted text preview: • Helps stabilize protein in membrane. K + Ion Channel • Homotetrameric protein. Ion pore made between the four monomers. • Each monomer is made of 2 transmembrane helices, 1 pore helix and a cytosolic tail. • Selectivity Filter – formed from the backbone carbonyl Oxygens from the loops connecting pore helix to the inner transmembrane helix. • The structure is stabilized by the packing of residues from the loop into the pore helix. Figure 12.10 Fig 12.9 Potassium Channel Tetramer Potassium Channel Tetramer K + Channel: Pore Helix and Filter How is the channel selective for K + ? The protein acts as surrogate Water K (OH 2 ) 8 + = hydration shell (8 H 2 O needed to stabilize K + ) Within the K + Ion Channel only: Resolvation Energy ~ Desolvation Energy Na (OH 2 ) 6 + = hydration shell (6 H 2 O needed to stabilize Na + ) Within the K + Ion Channel only: Resolvation Energy <<< Desolvation Energy Rapid ion flow through the selectivity filter is facilitated by ion-ion repuslion, with one ion pushing the next ion through the channel How is the channel selective for K + ?...
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• Helps stabilize protein in membrane K Ion Channel •...

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