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Forces and energetics of the canonical tetrameric cation channel gating.

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Title: Forces and energetics of the canonical tetrameric cation channel gating.
Authors: Scheuring, Simon1,2,3 sis2019@med.cornell.edu
Source: Proceedings of the National Academy of Sciences of the United States of America. 7/11/2023, Vol. 120 Issue 28, p1-9. 9p.
Subjects: Potential energy, Force & energy, Cations, Single molecules, Ion channels
Abstract: The canonical gating mechanism of tetrameric cation channels involves the spreading of the pore-lining helices at the so-called bundle-crossing gate. Despite a wealth of structural information, we lack a physical description of the gating process. Here, I took advantage of an entropic polymer stretching physical model and MthK structures to derive the forces and energies involved in pore-domain gating. In MthK, the Ca2+-induced conformational change in the RCK domain alone opens the bundle-crossing gate through pulling via unfolded linkers. In the open conformation, the linkers serve as entropic springs between the RCK domain and bundle-crossing gate that store an elastic potential energy of 3.6kBT and exert 9.8 pN (piconewton) radial pulling force to keep the gate open. I further derive that the work to load the linkers to prime the channel for opening is up to 3.8kBT, exerting up to 15.5 pN to pull the bundle-crossing open. Opening of the bundle-crossing leads to a release of 3.3kBT spring potential energy. Thus, the closed/RCK-apo and the open/RCK-Ca2+ conformations are separated by a barrier of several kBT. I discuss how these findings relate to the functional properties of MthK and suggest that given the architectural conservation of the helix–pore-loop–helix pore-domain among all tetrameric cation channels, these physical parameters might be quite general. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:The canonical gating mechanism of tetrameric cation channels involves the spreading of the pore-lining helices at the so-called bundle-crossing gate. Despite a wealth of structural information, we lack a physical description of the gating process. Here, I took advantage of an entropic polymer stretching physical model and MthK structures to derive the forces and energies involved in pore-domain gating. In MthK, the Ca2+-induced conformational change in the RCK domain alone opens the bundle-crossing gate through pulling via unfolded linkers. In the open conformation, the linkers serve as entropic springs between the RCK domain and bundle-crossing gate that store an elastic potential energy of 3.6kBT and exert 9.8 pN (piconewton) radial pulling force to keep the gate open. I further derive that the work to load the linkers to prime the channel for opening is up to 3.8kBT, exerting up to 15.5 pN to pull the bundle-crossing open. Opening of the bundle-crossing leads to a release of 3.3kBT spring potential energy. Thus, the closed/RCK-apo and the open/RCK-Ca2+ conformations are separated by a barrier of several kBT. I discuss how these findings relate to the functional properties of MthK and suggest that given the architectural conservation of the helix–pore-loop–helix pore-domain among all tetrameric cation channels, these physical parameters might be quite general. [ABSTRACT FROM AUTHOR]
ISSN:00278424
DOI:10.1073/pnas.2221616120