2d03

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Image:2d03.gif

2d03, resolution 1.97Å

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Crystal structure of the G91S mutant of the NNA7 Fab

Overview

The NNA7 Fab antibody fragment recognizes the human N-type blood-group antigen comprised of the N-terminal glycopeptide of glycophorin A (GPA). A mutant form of this Fab fragment, NNA7-G91S, exhibits markedly reduced antigen binding. To provide insight into how these Fab fragments recognize this glycopeptide antigen, the crystal structures of NNA7 and NNA7-G91S were solved and refined to 1.83 and 1.97 A resolution, respectively. Both molecules are composed of the same heavy (H) chain Fd fragment, but each contains a slightly different light (L) chain owing to the G91S substitution. Specifically, the G91S mutation pushes the backbone of the neighboring H chain away from complementarity-determining region 3 (CDR3) of the L-chain variable region, allowing an additional glycerol cryoprotectant molecule to enter the antigen-combining site near the putative location of O-linked glycosylation. Each Fab fragment also possesses a well defined 2-(N-morpholino)ethanesulfonic acid (MES) molecule trapped in its antigen-combining site, as well as a crystallographic symmetry-related molecule comprising an amino-acid sequence that is virtually identical to the N-terminus of GPA. The MES molecule interacts with the H-chain CDR in a manner reminiscent of antibody-carbohydrate complexes. These results suggest a model for recognition of the glycopeptide antigen that accounts for the deleterious effect of the G91S substitution.

About this Structure

2D03 is a Single protein structure of sequence from Mus musculus with , and as ligands. Full crystallographic information is available from OCA.

Reference

Crystallographic analysis of the NNA7 Fab and proposal for the mode of human blood-group recognition., Xie K, Song SC, Spitalnik SL, Wedekind JE, Acta Crystallogr D Biol Crystallogr. 2005 Oct;61(Pt 10):1386-94. Epub 2005, Sep 28. PMID:16204891

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