title: Use of single point mutations in domain I of beta 2-glycoprotein I to determine fine antigenic specificity of antiphospholipid autoantibodies.
abstract: Autoantibodies against beta(2)-glycoprotein I (beta(2)GPI) appear to be a critical feature of the antiphospholipid syndrome (APS). As determined using domain deletion mutants, human autoantibodies bind to the first of five domains present in beta(2)GPI. In this study the fine detail of the domain I epitope has been examined using 10 selected mutants of whole beta(2)GPI containing single point mutations in the first domain. The binding to beta(2)GPI was significantly affected by a number of single point mutations in domain I, particularly by mutations in the region of aa 40-43. Molecular modeling predicted these mutations to affect the surface shape and electrostatic charge of a facet of domain I. Mutation K19E also had an effect, albeit one less severe and involving fewer patients. Similar results were obtained in two different laboratories using affinity-purified anti-beta(2)GPI in a competitive inhibition ELISA and with whole serum in a direct binding ELISA. This study confirms that anti-beta(2)GPI autoantibodies bind to domain I, and that the charged surface patch defined by residues 40-43 contributes to a dominant target epitope.
authors.affiliation: La Jolla Pharmaceutical Co., San Diego, CA 92121, USA. mike.iverson@ljpc.com
authors.forename: G Michael
authors.initials: GM
authors.lastname: Iverson
authors.forename: Stephen
authors.initials: S
authors.lastname: Reddel
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Victoria
authors.forename: Keith A
authors.initials: KA
authors.lastname: Cockerill
authors.forename: Ying-Xia
authors.initials: YX
authors.lastname: Wang
authors.forename: Marc A
authors.initials: MA
authors.lastname: Marti-Renom
authors.forename: Andrej
authors.initials: A
authors.lastname: Sali
authors.forename: David M
authors.initials: DM
authors.lastname: Marquis
authors.forename: Steven A
authors.initials: SA
authors.lastname: Krilis
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Linnik
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D017152:Antibodies, Antiphospholipid / Q000097:blood / Q000378:metabolism*; D000911:Antibodies, Monoclonal / Q000097:blood / Q000378:metabolism; D016736:Antiphospholipid Syndrome / Q000276:immunology; D001120:Arginine / Q000235:genetics; D001666:Binding Sites, Antibody / Q000235:genetics; D001667:Binding, Competitive / Q000235:genetics / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D000939:Epitopes / Q000032:analysis / Q000276:immunology* / Q000378:metabolism; D005998:Glycine / Q000235:genetics; D006023:Glycoproteins / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D017354:Point Mutation; D017434:Protein Structure, Tertiary / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D055672:Static Electricity; D053482:beta 2-Glycoprotein I
chemical_list: D017152:Antibodies, Antiphospholipid; D000911:Antibodies, Monoclonal; D000939:Epitopes; D006023:Glycoproteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D053482:beta 2-Glycoprotein I; D001120:Arginine; D005998:Glycine