title: Pseudo-symmetry and twinning in crystals of homologous antibody Fv fragments.
abstract: A difference of seven conservative amino-acid substitutions between two single-chain antibodies (scFvs) specific for chlamydial lipopolysaccharide does not significantly affect their molecular structures or packing contacts, but dramatically affects their crystallization. The structure of the variable domain (Fv) of SAG173-04 was solved to 1.86 A resolution and an R(cryst) of 18.9% in space group P2(1)2(1)2(1). Crystals of the homologous SAG506-01 diffracted to 1.95 A resolution and appeared at first to have Patterson symmetry I4/m or P4/mmm; however, no solution could be found in space groups belonging to the former and refinement in the only solution corresponding to the latter (in space group P4(3)2(1)2) stalled at R(free) = 30.0%. Detailed examination of the diffraction data revealed that the crystal was likely to be twinned and that the correct space group was P2(1)2(1)2(1). Both translational pseudo-symmetry and pseudo-merohedral twinning were observed in one crystal of SAG506-01 and pseudo-merohedral twinning was observed for a second crystal. The final R factor for SAG506-01 after refinement in P2(1)2(1)2(1) was 20.5%.
authors.affiliation: University of Victoria, Department of Biochemistry and Microbiology, Victoria BC V8P 3P6, Canada.
authors.forename: Cory L
authors.initials: CL
authors.lastname: Brooks
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Blackler
authors.forename: Sandra
authors.initials: S
authors.lastname: Gerstenbruch
authors.forename: Paul
authors.initials: P
authors.lastname: Kosma
authors.forename: Sven
authors.initials: S
authors.lastname: Müller-Loennies
authors.forename: Helmut
authors.initials: H
authors.lastname: Brade
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Evans
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology; D002693:Chlamydiaceae; D003001:Cloning, Molecular; D022801:Complementarity Determining Regions / Q000737:chemistry* / Q000276:immunology; D003460:Crystallization; D000939:Epitopes; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000276:immunology; D008969:Molecular Sequence Data; D009154:Mutation; D019151:Peptide Library; D017434:Protein Structure, Tertiary; D013045:Species Specificity; D040681:Structural Homology, Protein; D013329:Structure-Activity Relationship
chemical_list: D000911:Antibodies, Monoclonal; D022801:Complementarity Determining Regions; D000939:Epitopes; D008070:Lipopolysaccharides; D019151:Peptide Library