3nk5

<StructureSection load='3nk5' size='340' side='right' caption='[[3nk5]], [[Resolution|resolution]] 2.40&Aring;' scene=''>

<table><tr><td colspan='2'>[[3nk5]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Ecoli Ecoli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3NK5 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3NK5 FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=BOG:B-OCTYLGLUCOSIDE'>BOG</scene></td></tr>

<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[1rc2|1rc2]], [[2o9f|2o9f]], [[3nka|3nka]], [[3nkc|3nkc]]</td></tr>

<tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">aqpZ, b0875, bniP, JW0859 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=83333 ECOLI])</td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=3nk5 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3nk5 OCA], [http://pdbe.org/3nk5 PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=3nk5 RCSB], [http://www.ebi.ac.uk/pdbsum/3nk5 PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=3nk5 ProSAT]</span></td></tr>

[[http://www.uniprot.org/uniprot/AQPZ_ECOLI AQPZ_ECOLI]] Channel that permits osmotically driven movement of water in both directions. It is involved in the osmoregulation and in the maintenance of cell turgor during volume expansion in rapidly growing cells. It mediates rapid entry or exit of water in response to abrupt changes in osmolarity.<ref>PMID:10400575</ref> <ref>PMID:10518952</ref> <ref>PMID:11493683</ref>

<scriptWhenChecked>select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/nk/3nk5_consurf.spt"</scriptWhenChecked>

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== Publication Abstract from PubMed ==

Aquaporins are transmembrane channels that facilitate the permeation of water and small, uncharged amphipathic molecules across cellular membranes. One distinct aquaporin subfamily contains pure water channels, whereas a second subfamily contains channels that conduct small alditols such as glycerol, in addition to water. Distinction between these substrates is central to aquaporin function, though the contributions of protein structural motifs required for selectivity are not yet fully characterized. To address this question, we sequentially engineered three signature amino acids of the glycerol-conducting subfamily into the Escherichia coli water channel aquaporin Z (AqpZ). Functional analysis of these mutant channels showed a decrease in water permeability but not the expected increase in glycerol conduction. Using X-ray crystallography, we determined the atomic resolution structures of the mutant channels. The structures revealed a channel surprisingly similar in size to the wild-type AqpZ pore. Comparison with measured rates of transport showed that, as the size of the selectivity filter region of the channel approaches that of water, channel hydrophilicity dominated water conduction energetics. In contrast, the major determinant of selectivity for larger amphipathic molecules such as glycerol was channel cross-section size. Finally, we find that, although the selectivity filter region is indeed central to substrate transport, other structural elements that do not directly interact with the substrates, such as the loop connecting helices M6 and M7, and the C loop between helices C4 and C5, play an essential role in facilitating selectivity.

 

<div class="pdbe-citations 3nk5" style="background-color:#fffaf0;"></div>

[[Category: Ecoli]]

[[Category: Connell, J D.O]]

[[Category: Finer-Moore, J S]]

[[Category: Savage, D F]]

[[Category: Stroud, R M]]

[[Category: Aquaporin]]

[[Category: Transport protein]]