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| | {{STRUCTURE_2q69| PDB=2q69 | SCENE= }} | | {{STRUCTURE_2q69| PDB=2q69 | SCENE= }} |
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| - | '''Crystal Structure of Nak channel D66N mutant'''
| + | ===Crystal Structure of Nak channel D66N mutant=== |
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| - | ==Overview==
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| - | Apparent blockage of monovalent cation currents by the permeating blocker Ca(2+) is a physiologically essential phenomenon relevant to cyclic nucleotide-gated (CNG) channels. The recently determined crystal structure of a bacterial homolog of CNG channel pores, the NaK channel, revealed a Ca(2+) binding site at the extracellular entrance to the selectivity filter. This site is not formed by the side-chain carboxylate groups from the conserved acidic residue, Asp-66 in NaK, conventionally thought to directly chelate Ca(2+) in CNG channels, but rather by the backbone carbonyl groups of residue Gly-67. Here we present a detailed structural analysis of the NaK channel with a focus on Ca(2+) permeability and blockage. Our results confirm that the Asp-66 residue, although not involved in direct chelation of Ca(2+), plays an essential role in external Ca(2+) binding. Furthermore, we give evidence for the presence of a second Ca(2+) binding site within the NaK selectivity filter where monovalent cations also bind, providing a structural basis for Ca(2+) permeation through the NaK pore. Compared with other Ca(2+)-binding proteins, both sites in NaK present a novel mode of Ca(2+) chelation, using only backbone carbonyl oxygen atoms from residues in the selectivity filter. The external site is under indirect control by an acidic residue (Asp-66), making it Ca(2+)-specific. These findings give us a glimpse of the possible underlying mechanisms allowing Ca(2+) to act both as a permeating ion and blocker of CNG channels and raise the possibility of a similar chemistry governing Ca(2+) chelation in Ca(2+) channels.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_17878296}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 17878296 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_17878296}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Metal transport]] | | [[Category: Metal transport]] |
| | [[Category: Tetramer]] | | [[Category: Tetramer]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 14:25:34 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 03:29:08 2008'' |
Revision as of 00:29, 29 July 2008
Template:STRUCTURE 2q69
Crystal Structure of Nak channel D66N mutant
Template:ABSTRACT PUBMED 17878296
About this Structure
2Q69 is a Single protein structure of sequence from Bacillus cereus. Full crystallographic information is available from OCA.
Reference
Structural insight into Ca2+ specificity in tetrameric cation channels., Alam A, Shi N, Jiang Y, Proc Natl Acad Sci U S A. 2007 Sep 25;104(39):15334-9. Epub 2007 Sep 18. PMID:17878296
Page seeded by OCA on Tue Jul 29 03:29:08 2008
