| Autor: |
Varikoti RA; Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA., Fonseka HYY; Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA., Kelly MS; Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA., Javidi A; Data Sciences, Janssen Research and Development, Spring House, PA 19477, USA., Damre M; Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA., Mullen S; Department of Chemistry, The College of Wooster, Wooster, OH 44691, USA., Nugent JL 4th; Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA., Gonzales CM; Biology Department, Iona College, New Rochelle, NY 10801, USA., Stan G; Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA., Dima RI; Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221, USA. |
| Abstrakt: |
Essential cellular processes of microtubule disassembly and protein degradation, which span lengths from tens of μm to nm, are mediated by specialized molecular machines with similar hexameric structure and function. Our molecular simulations at atomistic and coarse-grained scales show that both the microtubule-severing protein spastin and the caseinolytic protease ClpY, accomplish spectacular unfolding of their diverse substrates, a microtubule lattice and dihydrofolate reductase (DHFR), by taking advantage of mechanical anisotropy in these proteins. Unfolding of wild-type DHFR requires disruption of mechanically strong β-sheet interfaces near each terminal, which yields branched pathways associated with unzipping along soft directions and shearing along strong directions. By contrast, unfolding of circular permutant DHFR variants involves single pathways due to softer mechanical interfaces near terminals, but translocation hindrance can arise from mechanical resistance of partially unfolded intermediates stabilized by β-sheets. For spastin, optimal severing action initiated by pulling on a tubulin subunit is achieved through specific orientation of the machine versus the substrate (microtubule lattice). Moreover, changes in the strength of the interactions between spastin and a microtubule filament, which can be driven by the tubulin code, lead to drastically different outcomes for the integrity of the hexameric structure of the machine. |
