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Three-dimensional structure of two crystal forms of FabR19.9 from a monoclonal anti-arsonate antibody.

ABSTRACT: The three-dimensional structure of FabR19.9 from a well-characterized anti-p-azobenzenearsonate monoclonal antibody has been determined by x-ray diffraction techniques in two crystalline forms (I and II) to a resolution of 2.8 and 2.7 A, respectively. Essentially the same tertiary and quaternary structure of the Fab is observed in the two forms. The major difference resides in the intermolecular contacts, which are interpreted to favor an irreversible transition from the metastable form I to the more stable form II. The third complementarity-determining region of the heavy chain (H3) folds back over the combining site and requires rearrangement for hapten binding. This dynamic requirement on H3 is consistent with its mobility in the structure and can explain hapten binding to an otherwise inaccessible antibody combining site.

SUBMITTER: Lascombe MB

PROVIDER: S-EPMC50145 | biostudies-other | 1992 Oct

REPOSITORIES: biostudies-other

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Three-dimensional structure of two crystal forms of FabR19.9 from a monoclonal anti-arsonate antibody.

Lascombe M B MB Alzari P M PM Poljak R J RJ Nisonoff A A

Proceedings of the National Academy of Sciences of the United States of America 19921001 20

The three-dimensional structure of FabR19.9 from a well-characterized anti-p-azobenzenearsonate monoclonal antibody has been determined by x-ray diffraction techniques in two crystalline forms (I and II) to a resolution of 2.8 and 2.7 A, respectively. Essentially the same tertiary and quaternary structure of the Fab is observed in the two forms. The major difference resides in the intermolecular contacts, which are interpreted to favor an irreversible transition from the metastable form I to the ...[more]

PMID: 1409652

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Project description:BackgroundMany antibody crystal structures have been solved. Structural modeling programs have been developed that utilize this information to predict 3-D structures of an antibody based upon its sequence. Because of the problem of self-reference, the accuracy and utility of these predictions can only be tested when a new structure has not yet been deposited in the Protein Data Bank.MethodsWe have solved the crystal structure of the Fab fragment of RAC18, a protective anti-ricin mAb, to 1.9 Å resolution. We have also modeled the Fv structure of RAC18 using publicly available Ab modeling tools Prediction of Immunoglobulin Structures (PIGS), RosettaAntibody, and Web Antibody Modeling (WAM). The model structures underwent energy minimization. We compared results to the crystal structure on the basis of root-mean-square deviation (RMSD), template modeling score (TM-score), Z-score, and MolProbity analysis.FindingsThe crystal structure showed a pocket formed mainly by AA residues in each of the heavy chain complementarity determining regions (CDRs). There were differences between the crystal structure and structures predicted by the modeling tools, particularly in the CDRs. There were also differences among the predicted models, although the differences were small and within experimental error. No one modeling program was clearly superior to the others. In some cases, choosing structures based only on sequence homology to the crystallized Ab yielded RMSDs comparable to the models.ConclusionsMolecular modeling programs accurately predict the structure of most regions of antibody variable domains of RAC18. The hypervariable CDRs proved most difficult to model, particularly H chain CDR3. Because CDR3 is most often involved in contact with antigen, this defect must be considered when using models to identify potential contacts between antibody and antigen. Because this study represents only a single case, the results cannot be generalized. Rather they highlight the utility and limitations of modeling programs.

Dataset Information

Three-dimensional structure of two crystal forms of FabR19.9 from a monoclonal anti-arsonate antibody.

Publications

Three-dimensional structure of two crystal forms of FabR19.9 from a monoclonal anti-arsonate antibody.

Similar Datasets

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