4jta
From Proteopedia
Crystal structure of Kv1.2-2.1 paddle chimera channel in complex with Charybdotoxin
Structural highlights
Function[KCAB2_RAT] Accessory potassium channel protein which modulates the activity of the pore-forming alpha subunit. [KAX11_LEIQH] Potent selective inhibitor of high conductance (maxi-K), different medium and small conductance calcium-activated potassium channels (KCa/KCNM), as well as a voltage-dependent potassium channel (Kv1.3/KCNA3). It appears to block channel activity by a simple bimolecular inhibition process.[1] Has a pH-specific antimicrobial activity against bacteria (B.subtilis, E.coli and S.aureus) and the fungus C.albicans.[2] [KCNA2_RAT] Mediates the voltage-dependent potassium ion permeability of excitable membranes. Assuming opened or closed conformations in response to the voltage difference across the membrane, the protein forms a potassium-selective channel through which potassium ions may pass in accordance with their electrochemical gradient.[3] Publication Abstract from PubMedPore-blocking toxins inhibit voltage-dependent K(+) channels (Kv channels) by plugging the ion-conduction pathway. We have solved the crystal structure of paddle chimera, a Kv channel in complex with charybdotoxin (CTX), a pore-blocking toxin. The toxin binds to the extracellular pore entryway without producing discernable alteration of the selectivity filter structure and is oriented to project its Lys27 into the pore. The most extracellular K(+) binding site (S1) is devoid of K(+) electron-density when wild-type CTX is bound, but K(+) density is present to some extent in a Lys27Met mutant. In crystals with Cs(+) replacing K(+), S1 electron-density is present even in the presence of Lys27, a finding compatible with the differential effects of Cs(+) vs K(+) on CTX affinity for the channel. Together, these results show that CTX binds to a K(+) channel in a lock and key manner and interacts directly with conducting ions inside the selectivity filter. DOI:http://dx.doi.org/10.7554/eLife.00594.001. Structure of a pore-blocking toxin in complex with a eukaryotic voltage-dependent K(+) channel.,Banerjee A, Lee A, Campbell E, Mackinnon R Elife. 2013 May 21;2:e00594. doi: 10.7554/eLife.00594. Print 2013. PMID:23705070[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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