Biomaterial Database

Three-dimensional structure of an antigen-antibody complex at 6 A resolution. 1985

A G Amit, and R A Mariuzza, and S E Phillips, and R J Poljak

Present understanding of the three-dimensional structure of antibody combining sites is based on X-ray diffraction studies of myeloma immunoglobulins. The structures of the antigen-binding fragment (Fab) complexes of two of these immunoglobulins with small ligands have also been determined. However, there is no crystallographic information concerning the interactions of an antibody with an antigen, nor do we know the precise structure of antigenic determinants on protein molecules. We now report the first structure determination of an antigen-antibody complex at 6 A resolution. The structure of the complex between hen egg-white lysozyme and the Fab of a monoclonal anti-lysozyme antibody (D1.3) shows that the combining site of antibodies is not merely a cleft delineated by the complementarity-determining regions of the variable regions of the light and heavy chains, but is a larger area extending beyond it. A correspondingly large area of the antigen makes close contacts with the antibody, in agreement with the notion of a 'topographical' rather than 'sequential' antigenic determinant. The structural basis of cross-reactivities of an antibody with heterologous antigens and the effect of a single amino acid substitution on antigenic specificity can thus be visualized in the structural model presented here.

UI	MeSH Term	Description	Entries
D007140	Immunoglobulin Fab Fragments	Univalent antigen-binding fragments composed of one entire IMMUNOGLOBULIN LIGHT CHAIN and the amino terminal end of one of the IMMUNOGLOBULIN HEAVY CHAINS from the hinge region, linked to each other by disulfide bonds. Fab contains the IMMUNOGLOBULIN VARIABLE REGIONS, which are part of the antigen-binding site, and the first IMMUNOGLOBULIN CONSTANT REGIONS. This fragment can be obtained by digestion of immunoglobulins with the proteolytic enzyme PAPAIN.	Fab Fragment,Fab Fragments,Ig Fab Fragments,Immunoglobulins, Fab Fragment,Fab Immunoglobulin Fragments,Immunoglobulin Fab Fragment,Immunoglobulins, Fab,Fab Fragment Immunoglobulins,Fab Fragment, Immunoglobulin,Fab Fragments, Immunoglobulin,Fragment Immunoglobulins, Fab,Fragment, Fab,Immunoglobulin Fragments, Fab
D008958	Models, Molecular	Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.	Molecular Models,Model, Molecular,Molecular Model
D009113	Muramidase	A basic enzyme that is present in saliva, tears, egg white, and many animal fluids. It functions as an antibacterial agent. The enzyme catalyzes the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrin. EC 3.2.1.17.	Lysozyme,Leftose,N-Acetylmuramide Glycanhydrolase,Glycanhydrolase, N-Acetylmuramide,N Acetylmuramide Glycanhydrolase
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D000936	Antigen-Antibody Complex	The complex formed by the binding of antigen and antibody molecules. The deposition of large antigen-antibody complexes leading to tissue damage causes IMMUNE COMPLEX DISEASES.	Immune Complex,Antigen-Antibody Complexes,Immune Complexes,Antigen Antibody Complex,Antigen Antibody Complexes,Complex, Antigen-Antibody,Complex, Immune,Complexes, Antigen-Antibody,Complexes, Immune
D014961	X-Ray Diffraction	The scattering of x-rays by matter, especially crystals, with accompanying variation in intensity due to interference effects. Analysis of the crystal structure of materials is performed by passing x-rays through them and registering the diffraction image of the rays (CRYSTALLOGRAPHY, X-RAY). (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Xray Diffraction,Diffraction, X-Ray,Diffraction, Xray,Diffractions, X-Ray,Diffractions, Xray,X Ray Diffraction,X-Ray Diffractions,Xray Diffractions
D046911	Macromolecular Substances	Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.	Macromolecular Complexes,Macromolecular Compounds,Macromolecular Compounds and Complexes,Complexes, Macromolecular,Compounds, Macromolecular,Substances, Macromolecular
D051379	Mice	The common name for the genus Mus.	Mice, House,Mus,Mus musculus,Mice, Laboratory,Mouse,Mouse, House,Mouse, Laboratory,Mouse, Swiss,Mus domesticus,Mus musculus domesticus,Swiss Mice,House Mice,House Mouse,Laboratory Mice,Laboratory Mouse,Mice, Swiss,Swiss Mouse,domesticus, Mus musculus