title: Untying knots in proteins.
abstract: A shoelace can be readily untied by pulling its ends rather than its loops. Attempting to untie a native knot in a protein can also succeed or fail depending on where one pulls. However, thermal fluctuations induced by the surrounding water affect conformations stochastically and may add to the uncertainty of the outcome. When the protein is pulled by the termini, the knot can only get tightened, and any attempt at untying results in failure. We show that, by pulling specific amino acids, one may easily retract a terminal segment of the backbone from the knotting loop and untangle the knot. At still other amino acids, the outcome of pulling can go either way. We study the dependence of the untying probability on the way the protein is grasped, the pulling speed, and the temperature. Elucidation of the mechanisms underlying this dependence is critical for a successful experimental realization of protein knot untying.
authors.affiliation: Center for Theoretical Biological Physics, University of California-San Diego, 9500 Gilman Drive, La Jolla, California 92037, USA. jsulkow@physics.ucsd.edu
authors.forename: Joanna I
authors.initials: JI
authors.lastname: Sułkowska
authors.forename: Piotr
authors.initials: P
authors.lastname: Sułkowski
authors.forename: Piotr
authors.initials: P
authors.lastname: Szymczak
authors.forename: Marek
authors.initials: M
authors.lastname: Cieplak
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D011506:Proteins