1ine

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spinqualitylabelsall models 1ine, resolution 2.8Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

HOW THE ANTI-(METAL CHELATE) ANTIBODY CHA255 IS SPECIFIC FOR THE METAL ION OF ITS ANTIGEN: X-RAY STRUCTURES FOR TWO FAB'(SLASH)HAPTEN COMPLEXES WITH DIFFERENT METALS IN THE CHELATE

Overview

Antibodies with bound metal-chelate haptens provide new means for, exploiting the diverse properties of metallic elements. The murine, monoclonal antibody CHA255 (IgG1 lambda) binds the metal-chelate hapten, indium (III)-4-[N'-(2-hydroxyethyl)thioureido]-L-benzyl-EDTA (designated, In-EOTUBE) with high affinity (K(a) = 1.1 x 10(10) M-1). Antibody binding, is highly specific for the indium chelate; the affinity decreases as much, as 10(4) with other metals, even those having ionic radii close to indium., To better understand this selectivity, the crystal structure of the, antigen-binding fragment (Fab') of CHA255 complexed with its hapten, In(III)-EOTUBE, was determined by molecular replacement and refined at, 2.2-A resolution. The structure of CHA255 Fab' complexed with, Fe(III)-EOTUBE was also determined and refined at 2.8-A resolution. In, both structures, the hapten's EDTA moiety is half-buried near the center, of the complementarity-determining regions (CDR's). Five of the six CDR's, on the Fab' interact with the hapten through protein side-chain atoms (but, not main-chain atoms). A novel feature of the In-EOTUBE/Fab' complex is, coordination of the indium by N epsilon of one histidine from the heavy, chain's third CDR (distance = 2.4 A). The histidine coordination is not, observed in the Fe-EOTUBE/Fab' complex, due mainly to a slightly different, hapten conformation that reduces metal accessibility; this may partially, explain the 20-fold lower affinity of CHA255 for iron hapten. An, unexpected feature of the Fab' overall is an elbow angle of 193 degrees, (the angle between the pseudodyad axes of the Fab's constant and variable, domains).

About this Structure

1INE is a Protein complex structure of sequences from Mus musculus with and as ligands. Full crystallographic information is available from OCA.

Reference

How the anti-(metal chelate) antibody CHA255 is specific for the metal ion of its antigen: X-ray structures for two Fab'/hapten complexes with different metals in the chelate., Love RA, Villafranca JE, Aust RM, Nakamura KK, Jue RA, Major JG Jr, Radhakrishnan R, Butler WF, Biochemistry. 1993 Oct 19;32(41):10950-9. PMID:8218161

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