2abm
From Proteopedia
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'''Crystal Structure of Aquaporin Z Tetramer Reveals both Open and Closed Water-conducting Channels''' | '''Crystal Structure of Aquaporin Z Tetramer Reveals both Open and Closed Water-conducting Channels''' | ||
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[[Category: Fu, D.]] | [[Category: Fu, D.]] | ||
[[Category: Jiang, J.]] | [[Category: Jiang, J.]] | ||
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| - | [[Category: | + | [[Category: Membrane protein]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 18:51:15 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 15:51, 3 May 2008
Crystal Structure of Aquaporin Z Tetramer Reveals both Open and Closed Water-conducting Channels
Overview
AqpZ is a homotetramer of four water-conducting channels that facilitate rapid water movements across the plasma membrane of Escherichia coli. Here we report a 3.2 angstroms crystal structure of the tetrameric AqpZ (tAqpZ). All channel-lining residues in the four monomeric channels are found orientated in nearly identical positions with one marked exception at the narrowest channel constriction, where the side chain of a highly conserved Arg-189 adopts two distinct conformational orientations. In one of the four monomers, the guanidino group of Arg-189 points toward the periplasmic vestibule, opening up the constriction to accommodate the binding of a water molecule through a tridentate H-bond. In the other three monomers, the Arg-189 guanidino group bends over to form an H-bond with carbonyl oxygen of the Thr-183, thus occluding the channel. Therefore, the tAqpZ structure reveals two distinct Arg-189 confirmations associated with water permeation through the channel constrictions. Alternation between the two Arg-189 conformations disrupts continuous flow of water, thus regulating the open probability of the water pore. Further, the difference in Arg-189 displacements is correlated with a strong electron density found between the first transmembrane helices of two open channels, suggesting that the observed Arg-189 conformations are stabilized by asymmetrical subunit interactions in tAqpZ.
About this Structure
2ABM is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Crystal structure of AqpZ tetramer reveals two distinct Arg-189 conformations associated with water permeation through the narrowest constriction of the water-conducting channel., Jiang J, Daniels BV, Fu D, J Biol Chem. 2006 Jan 6;281(1):454-60. Epub 2005 Oct 20. PMID:16239219 Page seeded by OCA on Sat May 3 18:51:15 2008
