title: Mechanical unfolding of acylphosphatase studied by single-molecule force spectroscopy and MD simulations.
abstract: Single-molecule manipulation methods provide a powerful means to study protein transitions. Here we combined single-molecule force spectroscopy and steered molecular-dynamics simulations to study the mechanical properties and unfolding behavior of the small enzyme acylphosphatase (AcP). We find that mechanical unfolding of AcP occurs at relatively low forces in an all-or-none fashion and is decelerated in the presence of a ligand, as observed in solution measurements. The prominent energy barrier for the transition is separated from the native state by a distance that is unusually long for alpha/beta proteins. Unfolding is initiated at the C-terminal strand (beta(T)) that lies at one edge of the beta-sheet of AcP, followed by unraveling of the strand located at the other. The central strand of the sheet and the two helices in the protein unfold last. Ligand binding counteracts unfolding by stabilizing contacts between an arginine residue (Arg-23) and the catalytic loop, as well as with beta(T) of AcP, which renders the force-bearing units of the protein resistant to force. This stabilizing effect may also account for the decelerated unfolding of ligand-bound AcP in the absence of force.
authors.affiliation: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Gali
authors.initials: G
authors.lastname: Arad-Haase
authors.forename: Silvia G
authors.initials: SG
authors.lastname: Chuartzman
authors.forename: Shlomi
authors.initials: S
authors.lastname: Dagan
authors.forename: Reinat
authors.initials: R
authors.lastname: Nevo
authors.forename: Maksim
authors.initials: M
authors.lastname: Kouza
authors.forename: Binh Khanh
authors.initials: BK
authors.lastname: Mai
authors.forename: Hung Tien
authors.initials: HT
authors.lastname: Nguyen
authors.forename: Mai Suan
authors.initials: MS
authors.lastname: Li
authors.forename: Ziv
authors.initials: Z
authors.lastname: Reich
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000737:chemistry*; D000818:Animals; D001696:Biomechanical Phenomena; D007700:Kinetics; D008024:Ligands; D056004:Molecular Dynamics Simulation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012996:Solutions; D013057:Spectrum Analysis; D000097024:Acylphosphatase
chemical_list: D017766:Acid Anhydride Hydrolases; D008024:Ligands; D012996:Solutions; D000097024:Acylphosphatase