title: New general approach for determining the solution structure of a ligand bound weakly to a receptor: structure of a fibrinogen Aalpha-like peptide bound to thrombin (S195A) obtained using NOE distance constraints and an ECEPP/3 flexible docking program.
abstract: A new approach incorporating flexible docking simulations and NMR data is presented for calculating the bound conformation of a ligand that interacts weakly with an enzyme. This approach consists of sampling directly the conformation of a flexible ligand inside a receptor active site containing surrounding flexible loops. To make this sampling efficient, a ligand-growing procedure has been adopted. Optimization of the ECEPP/3-plus-NOE constraint function is carried out by using a collective variable Monte Carlo minimization technique. Numerous energy minimizations are made possible for such a large system by using a Bezier splines energy grid technique. This new flexible docking approach was applied to determine the structure of a fibrinogen Aalpha-like peptide (7DFLAEGGGVRGPRV20) bound to an active site mutant of thrombin [thrombin(S195A)]. Structure calculations of the bound ligand, using 2D-transferred NOESY distance constraints in the DIANA program, showed that the N-terminal portion of the peptide (D7-R16) involves a chain reversal, whereas the C-terminal portion (G17-V20) adopts a fold that exists in several different orientations. In addition, the ECEPP/3 flexible docking package was used to assess the conformational variability of the ligand and surrounding 60D-insertion loop of thrombin. Amino acid residues (17-20) of the peptide interact with a region of the enzyme that exhibits broad specificity, with a preferred direction between the 60D-insertion loop and Pro37 of thrombin.
authors.affiliation: Baker Laboratory of Chemistry, Cornell University, Ithaca, New York 14853-1301, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Maurer
authors.forename: J Y
authors.initials: JY
authors.lastname: Trosset
authors.forename: C C
authors.initials: CC
authors.lastname: Lester
authors.forename: E E
authors.initials: EE
authors.lastname: DiBella
authors.forename: H A
authors.initials: HA
authors.lastname: Scheraga
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002942:Circular Dichroism; D003198:Computer Simulation; D004926:Escherichia coli / Q000737:chemistry; D005340:Fibrinogen / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D009010:Monte Carlo Method; D010957:Plasmids; D017354:Point Mutation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins; D013917:Thrombin / Q000737:chemistry*
chemical_list: D008024:Ligands; D011994:Recombinant Proteins; D005340:Fibrinogen; D013917:Thrombin