6w0b | pdb_00006w0b

Open-gate KcsA soaked in 2 mM BaCl2

spinqualitylabelsall models 6w0b, resolution 3.60Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6w0b is a 3 chain structure with sequence from "actinomyces_lividans"_krasil'nikov_et_al._1965 "actinomyces lividans" krasil'nikov et al. 1965 and Buffalo rat. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: BA, K Gene: kcsA, skc1 ("Actinomyces lividans" Krasil'nikov et al. 1965) Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [KCSA_STRLI] Acts as a pH-gated potassium ion channel; changing the cytosolic pH from 7 to 4 opens the channel, although it is not clear if this is the physiological stimulus for channel opening. Monovalent cation preference is K(+) > Rb(+) > NH4(+) >> Na(+) > Li(+). Publication Abstract from PubMed Barium (Ba(2+)) is a classic permeant blocker of potassium (K(+)) channels. The "external lock-in effect" in barium block experiments, whereby the binding of external K(+) impedes the forward translocation of the blocker, provides a powerful avenue to investigate the selectivity of the binding sites along the pore of potassium channels. Barium block experiments show that the external lock-in site is highly selective for K(+) over Na(+). Wild-type KcsA was crystallized in low K(+) conditions, and the crystals were soaked in solutions containing various concentrations of barium. Structural analysis reveals open and closed gate conformations of the KcsA channel. Anomalous diffraction experiments show that Ba(2+) primarily binds to the innermost site S4 of the selectivity filter of the open-gate conformation and also the site S2, but no binding is detected with the closed-gate conformation. Alchemical free-energy perturbation calculations indicate that the presence of a Ba(2+) ion in the selectivity filter boosts the specificity of K(+) binding relative to Na(+) in the external sites S0-S2. Open and Closed Structures of a Barium-Blocked Potassium Channel.,Rohaim A, Gong L, Li J, Rui H, Blachowicz L, Roux B J Mol Biol. 2020 Aug 7;432(17):4783-4798. doi: 10.1016/j.jmb.2020.06.012. Epub, 2020 Jun 29. PMID:32615129 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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