Electrical unfolding of cytochrome c during translocation through a nanopore constriction.

Autor: Tripathi P; Department of Physics, Northeastern University, Boston, MA 02115., Benabbas A; Department of Physics, Northeastern University, Boston, MA 02115., Mehrafrooz B; Center for Biophysics and Quatitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801., Yamazaki H; Department of Physics, Northeastern University, Boston, MA 02115., Aksimentiev A; Center for Biophysics and Quatitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801.; Department of Physics and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801., Champion PM; Department of Physics, Northeastern University, Boston, MA 02115; p.champion@northeastern.edu wanunu@neu.edu.; Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA 02115., Wanunu M; Department of Physics, Northeastern University, Boston, MA 02115; p.champion@northeastern.edu wanunu@neu.edu.; Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA 02115.
Jazyk: angličtina
Zdroj: Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2021 Apr 27; Vol. 118 (17).
DOI: 10.1073/pnas.2016262118
Abstrakt: Many small proteins move across cellular compartments through narrow pores. In order to thread a protein through a constriction, free energy must be overcome to either deform or completely unfold the protein. In principle, the diameter of the pore, along with the effective driving force for unfolding the protein, as well as its barrier to translocation, should be critical factors that govern whether the process proceeds via squeezing, unfolding/threading, or both. To probe this for a well-established protein system, we studied the electric-field-driven translocation behavior of cytochrome c (cyt c ) through ultrathin silicon nitride (SiN x ) solid-state nanopores of diameters ranging from 1.5 to 5.5 nm. For a 2.5-nm-diameter pore, we find that, in a threshold electric-field regime of ∼30 to 100 MV/m, cyt c is able to squeeze through the pore. As electric fields inside the pore are increased, the unfolded state of cyt c is thermodynamically stabilized, facilitating its translocation. In contrast, for 1.5- and 2.0-nm-diameter pores, translocation occurs only by threading of the fully unfolded protein after it transitions through a higher energy unfolding intermediate state at the mouth of the pore. The relative energies between the metastable, intermediate, and unfolded protein states are extracted using a simple thermodynamic model that is dictated by the relatively slow (∼ms) protein translocation times for passing through the nanopore. These experiments map the various modes of protein translocation through a constriction, which opens avenues for exploring protein folding structures, internal contacts, and electric-field-induced deformability.
Competing Interests: The authors declare no competing interest.
Databáze: MEDLINE
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