Aquaporin 5 Tetramer
(based on 3D9S.pdb)
Before clicking, notice there is no center pore.
The 4 Distinct Aquaporin Monomers. The cyan and red residues are the amino and carboxyl terminal ends of the protein. Both of the terminal endings lie within the intracellular region.
The active sites are emphasized here with the gold residues in the four pores. The center pore is not available for water transport. It is believed to be involved in gas and ion exchange.
This model really shows the general hydrophobic nature of this membrane protein. The yellow residues presented are hydrophobic residues. The cyan and red terminal ends of the protein are noted since they both lie intracellularly. Be certain to rotate this molecule to see visualize the aquaporin sitting in the membrane.
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Aquaporin 1 Monomer (based on 1FQY.pdb)
One of the clues of the existence of a water channel came as a result of the mercuric ion binding to the green cysteine residue shown here. The mercuric binding to the cysteine residue plugs the pore and halts water transport.When the mercuric ion was removed, normal water movement was restored.
The active asparagine, proline, alanine site is shown here in magenta. These are the residues for changing the water molecules orientation as they pass through the pore. This change in orientation effectively prevents the hydrogen ions from being translocated through the pore as well. The blue histidine/argines act as a selectivity filter repelling protons and other cations.
This is the same model as shown in the active sites model above but cutting away the inactive residues. Note the hydrophobic yellow residues opposite the magenta NPA site. Also recognize that the residues have some freedom of movement. It is likely that the histidine swings more into the pore thus enhancing its effect. Rotate it to get a perspective of the pore and the channeling effect. Remember cyan and red terminal residues are intracellular.
Aquaporins have a very interesting symmetry as shown here with the helical structure of the molecule. Notice the 3.5 helices and the symmetry shown.
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Channel Architecture of Aquaporin 0 (based on 1YMG.pdb)
Queue of water molecules being translocated through the pore showing the backbone structure. Selectivity filter is in blue and the NPA site is highlighted in magenta. The cyan and red ends mark the amino and carboxyl terminal ends.
Queue of water molecules being translocated through the pore. Several helices were cut out to better show the interaction between the water molecules in the queue and the NPA site. The Selectivity filter is in blue and the NPA site is highlighted in magenta. The cyan and red ends mark the amino and carboxyl terminal ends.
Queue of water molecules being translocated through the pore...
Queue of water molecules being translocated through the pore, emphasizing the NPA site in magenta, and the selectivity filter in blue...
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