title: Crystal structure of the antigen-binding fragment of a monoclonal antibody specific for the multidrug-resistance-linked ABC transporter human P-glycoprotein.
abstract: P-glycoprotein (P-gp) is a polyspecific ATP-dependent transporter linked to multidrug resistance in cancers that plays important roles in the pharmacokinetics of a large number of drugs. The drug-resistance phenotype of P-gp can be modulated by the monoclonal antibody UIC2, which specifically recognizes human P-gp in a conformation-dependent manner. Here, the purification, sequence determination and high-resolution structure of the Fab fragment of UIC2 (UIC2/Fab) are reported. Purified UIC2/Fab binds human P-gp with a 1:1 stoichiometry. Crystals of UIC2/Fab are triclinic (space group P1), with unit-cell parameters a = 40.67, b = 44.91, c = 58.09 Å, α = 97.62, β = 99.10, γ = 94.09°, and diffracted X-rays to 1.6 Å resolution. The structure was determined by molecular replacement and refined to 1.65 Å resolution. The asymmetric unit contains one molecule of UIC2/Fab, which exhibits a positively charged antigen-binding surface, suggesting that it might recognize an oppositely charged extracellular epitope of P-gp.
authors.affiliation: National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA.
authors.forename: Lothar
authors.initials: L
authors.lastname: Esser
authors.affiliation: National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA.
authors.forename: Suneet
authors.initials: S
authors.lastname: Shukla
authors.affiliation: National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Zhou
authors.affiliation: National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA.
authors.forename: Suresh V
authors.initials: SV
authors.lastname: Ambudkar
authors.affiliation: National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA.
authors.forename: Di
authors.initials: D
authors.lastname: Xia
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry* / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D000941:Antigens / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D015870:Gene Expression; D006801:Humans; D006825:Hybridomas / Q000737:chemistry; D007140:Immunoglobulin Fab Fragments / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D000941:Antigens; D007140:Immunoglobulin Fab Fragments; D011994:Recombinant Proteins
keywords: UIC2/Fab; human ABC-dependent transporter P-glycoprotein; monoclonal antibodies; multidrug resistance