4zbm

Crystal structure of Drosophila cyclic nucleotide gated channel pore mimicking NaK mutant

spinqualitylabelsall models 4zbm, resolution 1.90Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4zbm is a 2 chain structure with sequence from Baccr. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: BA, K Gene: BC_0669 (BACCR) Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Calcium permeability and the concomitant calcium block of monovalent ion current ("Ca2+ block") are properties of cyclic nucleotide-gated (CNG) channel fundamental to visual and olfactory signal transduction. Although most CNG channels bear a conserved glutamate residue crucial for Ca2+ block, the degree of block displayed by different CNG channels varies greatly. For instance, the Drosophila melanogaster CNG channel shows only weak Ca2+ block despite the presence of this glutamate. We previously constructed a series of chimeric channels in which we replaced the selectivity filter of the bacterial nonselective cation channel NaK with a set of CNG channel filter sequences and determined that the resulting NaK2CNG chimeras displayed the ion selectivity and Ca2+ block properties of the parent CNG channels. Here, we used the same strategy to determine the structural basis of the weak Ca2+ block observed in the Drosophila CNG channel. The selectivity filter of the Drosophila CNG channel is similar to that of most other CNG channels except that it has a threonine at residue 318 instead of a proline. We constructed a NaK chimera, which we called NaK2CNG-Dm, which contained the Drosophila selectivity filter sequence. The high resolution structure of NaK2CNG-Dm revealed a filter structure different from those of NaK and all other previously investigated NaK2CNG chimeric channels. Consistent with this structural difference, functional studies of the NaK2CNG-Dm chimeric channel demonstrated a loss of Ca2+ block compared with other NaK2CNG chimeras. Moreover, mutating the corresponding threonine (T318) to proline in Drosophila CNG channels increased Ca2+ block by 16 times. These results imply that a simple replacement of a threonine for a proline in Drosophila CNG channels has likely given rise to a distinct selectivity filter conformation that results in weak Ca2+ block. Structural implications of weak Ca2+ block in Drosophila cyclic nucleotide-gated channels.,Lam YL, Zeng W, Derebe MG, Jiang Y J Gen Physiol. 2015 Aug 17. pii: jgp.201511431. PMID:26283200 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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