4ms2

Structural basis of Ca2+ selectivity of a voltage-gated calcium channel

spinqualitylabelsall models 4ms2, resolution 2.75Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4ms2 is a 4 chain structure with sequence from Aliarcobacter butzleri RM4018. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CA, PX4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function A8EVM5_ALIB4 Publication Abstract from PubMed Voltage-gated calcium (CaV) channels catalyse rapid, highly selective influx of Ca2+ into cells despite a 70-fold higher extracellular concentration of Na+. How CaV channels solve this fundamental biophysical problem remains unclear. Here we report physiological and crystallographic analyses of a calcium selectivity filter constructed in the homotetrameric bacterial NaV channel NaVAb. Our results reveal interactions of hydrated Ca2+ with two high-affinity Ca2+-binding sites followed by a third lower-affinity site that would coordinate Ca2+ as it moves inward. At the selectivity filter entry, Site 1 is formed by four carboxyl side chains, which have a critical role in determining Ca2+ selectivity. Four carboxyls plus four backbone carbonyls form Site 2, which is targeted by the blocking cations Cd2+ and Mn2+, with single occupancy. The lower-affinity Site 3 is formed by four backbone carbonyls alone, which mediate exit into the central cavity. This pore architecture suggests a conduction pathway involving transitions between two main states with one or two hydrated Ca2+ ions bound in the selectivity filter and supports a 'knock-off' mechanism of ion permeation through a stepwise-binding process. The multi-ion selectivity filter of our CaVAb model establishes a structural framework for understanding the mechanisms of ion selectivity and conductance by vertebrate CaV channels. Structural basis for Ca selectivity of a voltage-gated calcium channel.,Tang L, Gamal El-Din TM, Payandeh J, Martinez GQ, Heard TM, Scheuer T, Zheng N, Catterall WA Nature. 2013 Nov 24. doi: 10.1038/nature12775. PMID:24270805 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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