title: In vitro polymerization of microtubules with a fullerene derivative.
abstract: Fullerene derivative C(60)(OH)(20) inhibited microtubule polymerization at low micromolar concentrations. The inhibition was mainly attributed to the formation of hydrogen bonding between the nanoparticle and the tubulin heterodimer, the building block of the microtubule, as evidenced by docking and molecular dynamics simulations. Our circular dichroism spectroscopy measurement indicated changes in the tubulin secondary structures, while our guanosine-5'-triphosphate hydrolysis assay showed hindered release of inorganic phosphate by the nanoparticle. Isothermal titration calorimetry revealed that C(60)(OH)(20) binds to tubulin at a molar ratio of 9:1 and with a binding constant of 1.3 ± 0.16 × 10(6) M(-1), which was substantiated by the binding site and binding energy analysis using docking and molecular dynamics simulations. Our simulations further suggested that occupancy by the nanoparticles at the longitudinal contacts between tubulin dimers within a protofilament or at the lateral contacts of the M-loop and H5 and H12 helices of neighboring tubulins could also influence the polymerization process. This study offered a new molecular-level insight on how nanoparticles may reshape the assembly of cytoskeletal proteins, a topic of essential importance for illuminating cell response to engineered nanoparticles and for the advancement of nanomedicine.
authors.affiliation: Laboratory of Single-Molecule Biophysics and Polymer Physics, COMSET, Clemson University, Clemson, South Carolina 29631, USA.
authors.forename: Tatsiana A
authors.initials: TA
authors.lastname: Ratnikova
authors.forename: Praveen Nedumpully
authors.initials: PN
authors.lastname: Govindan
authors.forename: Emppu
authors.initials: E
authors.lastname: Salonen
authors.forename: Pu Chun
authors.initials: PC
authors.lastname: Ke
mesh_terms: D004305:Dose-Response Relationship, Drug; D037741:Fullerenes / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006860:Hydrogen Bonding; D006868:Hydrolysis / Q000187:drug effects; D008870:Microtubules / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D058105:Polymerization / Q000187:drug effects*; D017433:Protein Structure, Secondary / Q000187:drug effects; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism
chemical_list: D037741:Fullerenes; D014404:Tubulin; D006160:Guanosine Triphosphate; C069837:fullerene C60