3E8U: Crystal Structure And Thermodynamic Analysis Of Diagnostic Fab 106.3 Complexed With Bnp 5-13 (c10a) Reveal Basis Of Selective Molecular Recognition

Citation:
Abstract
B-type natriuretic peptide (BNP) is a naturally secreted regulatory hormone that influences blood pressure and vascular water retention in human physiology. The plasma BNP concentration is a clinically recognized biomarker for various cardiovascular diseases. Quantitative detection of BNP can be achieved in immunoassays using the high-affinity monoclonal IgG1 antibody 106.3, which binds an epitope spanning residues 5-13 of the mature bioactive peptide. To understand the structural basis of this molecular recognition, we crystallized the Fab fragment complexed with the peptide epitope and determined the three-dimensional structure by X-ray diffraction to 2.1 A resolution. The structure reveals the detailed interactions that five of the complementarity-determining regions make with the partially folded peptide. Thermodynamic measurements using fluorescence spectroscopy suggest that the interaction is enthalpy driven, with an overall change in free energy of binding, DeltaG = -54 kJ/mol, at room temperature. The parameters are interpreted on the basis of the structural information. The kinetics of binding suggest a diffusion-limited mechanism, whereby the peptide easily adopts a bound conformation upon interaction with the antibody. Moreover, comparative analysis with alanine-scanning results of the epitope explains the basis of selectivity for BNP over other related natriuretic peptides.
PDB ID: 3E8UDownload
MMDB ID: 75128
PDB Deposition Date: 2008/8/20
Updated in MMDB: 2017/11
Experimental Method:
x-ray diffraction
Resolution: 2.1  Å
Source Organism:
Mus musculus
Similar Structures:
Biological Unit for 3E8U: hexameric; determined by author and by software (PISA)
Molecular Components in 3E8U
Label Count Molecule
Proteins (6 molecules)
2
FAB 106.3 Heavy Chain
Molecule annotation
2
FAB 106.3 Light Chain
Molecule annotation
2
BNP Peptide Epitope
Molecule annotation
* Click molecule labels to explore molecular sequence information.

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