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Na+/Ca2+ selectivity in the bacterial voltage-gated sodium channel NavAb

Author(s): Ben Corry

Journal: PeerJ
ISSN 2167-8359

Volume: 1;
Start page: e16;
Date: 2013;
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Keywords: Ion channel | Ion selectivity | Molecular dynamics | Sodium channel | Action potential | Bacterial channel | Calcium channel | Simulation

The recent publication of a number of high resolution bacterial voltage-gated sodium channel structures has opened the door for the mechanisms employed by these channels to distinguish between ions to be elucidated. The way these channels select between Na+ and K+ has been investigated in computational studies, but the selectivity for Na+ over Ca2+ has not yet been studied in this way. Here we use molecular dynamics simulations to calculate the energetics of Na+ and Ca2+ transport through the channel. Single ion profiles show that Ca2+ experiences a large barrier midway through the selectivity filter that is not seen by Na+. This barrier is caused by the need for Ca2+ to partly dehydrate to pass through this region and the lack of compensating interactions with the protein. Multi-ion profiles show that ions can pass each other in the channel, which is why the presence of Ca2+ does not block Na+ conduction despite binding more strongly in the pore.
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