title: Computational approaches for identification of conserved/unique binding pockets in the A chain of ricin.
abstract: BACKGROUND
  Specific and sensitive ligand-based protein detection assays that employ antibodies or small molecules such as peptides, aptamers or other small molecules require that the corresponding surface region of the protein be accessible and that there be minimal cross-reactivity with non-target proteins. To reduce the time and cost of laboratory screening efforts for diagnostic reagents, we developed new methods for evaluating and selecting protein surface regions for ligand targeting.
  
  
  RESULTS
  We devised combined structure- and sequence-based methods for identifying 3D epitopes and binding pockets on the surface of the A chain of ricin that are conserved with respect to a set of ricin A chains and unique with respect to other proteins. We (1) used structure alignment software to detect structural deviations and extracted from this analysis the residue-residue correspondence, (2) devised a method to compare corresponding residues across sets of ricin structures and structures of closely related proteins, (3) devised a sequence-based approach to determine residue infrequency in local sequence context and (4) modified a pocket-finding algorithm to identify surface crevices in close proximity to residues determined to be conserved/unique based on our structure- and sequence-based methods. In applying this combined informatics approach to ricin A, we identified a conserved/unique pocket in close proximity (but not overlapping) the active site that is suitable for bi-dentate ligand development. These methods are generally applicable to identification of surface epitopes and binding pockets for development of diagnostic reagents, therapeutics and vaccines.
authors.affiliation: Lawrence Livermore National Laboratory 7000 E. Avenue, Livermore, CA 94550, USA. zhou4@llnl.gov
authors.forename: Carol L Ecale
authors.initials: CL
authors.lastname: Zhou
authors.forename: Adam T
authors.initials: AT
authors.lastname: Zemla
authors.forename: Diana
authors.initials: D
authors.lastname: Roe
authors.forename: Malin
authors.initials: M
authors.lastname: Young
authors.forename: Marisa
authors.initials: M
authors.lastname: Lam
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Schoeniger
authors.forename: Rod
authors.initials: R
authors.lastname: Balhorn
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D001665:Binding Sites; D003198:Computer Simulation; D017124:Conserved Sequence; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D012276:Ricin / Q000032:analysis* / Q000737:chemistry*; D016415:Sequence Alignment / Q000379:methods*; D020539:Sequence Analysis, Protein / Q000379:methods*; D017386:Sequence Homology, Amino Acid
chemical_list: D012276:Ricin