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Issue 36, 2012
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Interaction of C70fullerene with the Kv1.2 potassium channel

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Abstract

Fullerene C70 is known to partition into lipid membranes and change their physical properties. Together with gallic acid (GA), C70 induces cell contraction and cell death. How C70 and GA-induced perturbations of lipid membranes affect cellular function and membrane protein activity is not understood, though. Meanwhile, fullerene is also known to interfere with the activity of potassium channel proteins, but the mechanisms of protein inhibition are not known. Here we consider the possibility that membrane protein function would be inhibited by C70 and/or GA through direct contact or through lipid-mediated interactions. To this end, we use microsecond time scale atomistic simulations to explore (a) modifications of membrane properties in the presence of C70 and/or GA, and (b) the possible conformational changes in Kv1.2, a voltage-gated potassium channel, upon exposure to C70, or GA, or both. C70 is found to have an observable effect on structural and elastic properties of protein-free membranes, while the effects of GA on the membrane are less evident. Fullerene–GA interaction is strong and affects significantly the partitioning of C70 in the membrane, stabilizing C70 in the aqueous phase. When Kv1.2 is exposed to the solutes, only small conformational changes are observed on the microsecond time scale – comparable to the fluctuations observed in the absence of any solute. Blocking of the channel entrance is not observed, as fullerene binds mainly to hydrophobic residues, both in the water-exposed loops and in the transmembrane helices. The tilt angle of transmembrane helices in the voltage-sensing domain appears to be affected by direct contact with fullerene, but a generic effect due to the small increase in membrane thickness might also play a role. A small rotation of the S3 and S4 helices in the voltage-sensing domain is noticed when C70 is embedded in the membrane. The interpretation of the observed conformational changes is not straightforward due to the associated time scales, which are difficult to sample with state-of-the-art computing resources. We cannot exclude that both membrane-mediated interactions and specific protein–solute interactions affect the conformation of the protein.

Graphical abstract: Interaction of C70 fullerene with the Kv1.2 potassium channel

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Supplementary files

Article information


Submitted
31 Mar 2012
Accepted
08 Jun 2012
First published
08 Jun 2012

Phys. Chem. Chem. Phys., 2012,14, 12526-12533
Article type
Paper

Interaction of C70 fullerene with the Kv1.2 potassium channel

L. Monticelli, J. Barnoud, A. Orlowski and I. Vattulainen, Phys. Chem. Chem. Phys., 2012, 14, 12526
DOI: 10.1039/C2CP41117B

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