2AHY

Na+ complex of the NaK Channel

Summary for 2AHY

• Entry DOI: 10.2210/pdb2ahy/pdb
• Related: 2AHZ
• Descriptor: Potassium channel protein, SODIUM ION, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: inverted teepee, helix bundle, tetramer, central cavity, ion binding, transport protein
• Biological source: Bacillus cereus
• Total number of polymer chains: 2
• Total formula weight: 24857.43

Authors

Shi, N.,Ye, S.,Alam, A.,Chen, L.,Jiang, Y. (deposition date: 2005-07-28, release date: 2006-02-07, Last modification date: 2024-02-14)

Primary citation

Shi, N.,Ye, S.,Alam, A.,Chen, L.,Jiang, Y.
Atomic structure of a Na+- and K+-conducting channel.
Nature, 440:570-574, 2006

PubMed Abstract: 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.

PubMed: 16467789
DOI: 10.1038/nature04508

Experimental method

X-RAY DIFFRACTION (2.4 Å)