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| {{STRUCTURE_2ahz| PDB=2ahz | SCENE= }} | | {{STRUCTURE_2ahz| PDB=2ahz | SCENE= }} |
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| '''K+ complex of the NaK Channel'''
| | ===K+ complex of the NaK Channel=== |
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| ==Overview==
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| Ion selectivity is one of the basic properties that define an ion channel. Most tetrameric cation channels, which include the K+, Ca2+, Na+ and cyclic nucleotide-gated channels, probably share a similar overall architecture in their ion-conduction pore, but the structural details that determine ion selection are different. Although K+ channel selectivity has been well studied from a structural perspective, little is known about the structure of other cation channels. Here we present crystal structures of the NaK channel from Bacillus cereus, a non-selective tetrameric cation channel, in its Na+- and K+-bound states at 2.4 A and 2.8 A resolution, respectively. The NaK channel shares high sequence homology and a similar overall structure with the bacterial KcsA K+ channel, but its selectivity filter adopts a different architecture. Unlike a K+ channel selectivity filter, which contains four equivalent K+-binding sites, the selectivity filter of the NaK channel preserves the two cation-binding sites equivalent to sites 3 and 4 of a K+ channel, whereas the region corresponding to sites 1 and 2 of a K+ channel becomes a vestibule in which ions can diffuse but not bind specifically. Functional analysis using an 86Rb flux assay shows that the NaK channel can conduct both Na+ and K+ ions. We conclude that the sequence of the NaK selectivity filter resembles that of a cyclic nucleotide-gated channel and its structure may represent that of a cyclic nucleotide-gated channel pore.
| | The line below this paragraph, {{ABSTRACT_PUBMED_16467789}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 16467789 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_16467789}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Ion binding]] | | [[Category: Ion binding]] |
| [[Category: Tetramer]] | | [[Category: Tetramer]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 19:04:30 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 20:20:48 2008'' |
