title: Role of the linker domain and the 203-214 N-terminal residues in the human topoisomerase I DNA complex dynamics.
abstract: The influence of the N-terminal residues 203-214 and the linker domain on motions in the human topoisomerase I-DNA complex has been investigated by comparing the molecular dynamics simulations of the system with (topo70) or without (topo58/6.3) these regions. Topo58/6.3 is found to fluctuate more than topo70, indicating that the presence of the N-terminal residues and the linker domain dampen the core and C-terminal fluctuations. The simulations also show that residues 203-207 and the linker domain participate in a network of correlated movements with key regions of the enzyme, involved in the human topoisomerase I catalytic cycle, providing a structural-dynamical explanation for the better DNA relaxation activity of topo70 when compared to topo58/6.3. The data have been examined in relation to a wealth of biochemical, site-directed mutagenesis and crystallographic data on human topoisomerase I. The simulations finally show the occurrence of a network of direct and water mediated hydrogen bonds in the proximity of the active site, and the presence of a water molecule in the appropriate position to accept a proton from the catalytic Tyr-723 residue, suggesting that water molecules have an important role in the stabilization and function of this enzyme.
authors.affiliation: CASPUR, Consortium for Supercomputing in Research, Via dei Tizii 6b, Rome, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Chillemi
authors.forename: M
authors.initials: M
authors.lastname: Redinbo
authors.forename: A
authors.initials: A
authors.lastname: Bruselles
authors.forename: A
authors.initials: A
authors.lastname: Desideri
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D001665:Binding Sites; D003198:Computer Simulation; D004247:DNA / Q000737:chemistry*; D004264:DNA Topoisomerases, Type I / Q000737:chemistry*; D004789:Enzyme Activation; D006801:Humans; D006860:Hydrogen Bonding; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009038:Motion; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D004247:DNA; D004264:DNA Topoisomerases, Type I