Karl Decker, Martin Page, and Aleksei Aksimentiev.
Nanoscale ion pump derived from a biological water channel.
Journal of Physical Chemistry B, 121:7899-7906, 2017.
(PMC: PMC5570624)
DECK2017-AA
Biological molecular machines perform the work of supporting life at the
smallest of scales, including the work of shuttling ions across cell
boundaries and against chemical gradients. Systems of artificial channels
at the nanoscale can likewise control ionic concentration by way of ionic
current rectification, species selectivity, and voltage gating mechanisms.
Here, we theoretically show that a voltage-gated, ion species-selective,
and rectifying ion channel can be built using the components of a biological
water channel aquaporin. Through all-atom molecular dynamics
simulations, we show that the ionic conductance of a truncated aquaporin
channel nonlinearly increases with the bias magnitude, depends on the
channel's orientation, and is highly cation specific but only for one polarity
of the transmembrane bias. Further, we show that such an unusually
complex response of the channel to transmembrane bias arises from
mechanical motion of a positively charged gate that blocks cation
transport. By combining two truncated aquaporins, we demonstrate a
molecular system that pumps ions against their chemical gradients when
subject to an alternating transmembrane bias. Our work sets the stage for
future biomimicry efforts directed toward reproducing the function of
biological ion pumps using synthetic components.
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