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Complex between Peptostreptococcusmagnus ProteinL and a human antibody reveals structural convergence in the interaction modes of fab binding proteins

Record type: Article

Background: Peptostreptococcus magnus protein L (PpL) is a multidomain, bacterial surface protein whose presence correlates with virulence. It consists of up to five homologous immunoglobulin binding domains that interact with the variable (V-L) regions of kappa light chains found on two thirds of mammalian antibodies.
Results: We refined the crystal structure of the complex between a human antibody Fab fragment (2A2) and a single PpL domain (61 residues) to 2.7 Angstrom. The asymmetric unit contains two Fab molecules sandwiching a single PpL domain, which contacts similar V-L framework regions of two light chains via independent interfaces. The residues contacted on V-L are remote from the hypervariable loops. One PpL-V-K interface agrees with previous biochemical data, while the second is novel. Site-directed mutagenesis and analytical-centrifugation studies suggest that the two PpL binding sites have markedly different affinities for V-L. The PpL residues in both interactions are well conserved among different Peptostreptococcus magnus strains. The Fab contact positions identified in the complex explain the high specificity of PpL for antibodies with kappa rather than lambda chains.
Conclusions: The PpL-Fab complex shows the first interaction of a bacterial virulence factor with a Fab light chain outside the conventional combining site. Structural comparison with two other bacterial proteins interacting with the Fab heavy chain shows that PpL, structurally homologous to streptococcal SpG domains, shares with the latter a similar binding mode. These two bacterial surface proteins interact with their respective immunoglobulin regions through a similar beta zipper interaction.

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Citation

Graille, M., Stura, E.A., Housden, N.G., Bottomley, S.P., Beale, D., Taussig, M.J., Sutton, B.J., Gore, M.G. and Charbonnier, J.-B. (2001) Complex between Peptostreptococcusmagnus ProteinL and a human antibody reveals structural convergence in the interaction modes of fab binding proteins Structure, 9, (8), pp. 679-687. (doi:10.1016/S0969-2126(01)00630-X).

More information

Submitted date: 22 March 2001
Keywords: immunoglobulin binding proteins (IBP), antibody complex, cell surface protein, X-ray structure

Identifiers

Local EPrints ID: 25148
URI: http://eprints.soton.ac.uk/id/eprint/25148
ISSN: 0969-2126
PURE UUID: 89bf6574-a914-4a1a-ab55-ea7f5a9f35f1

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Date deposited: 06 Apr 2006
Last modified: 17 Jul 2017 16:11

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Contributors

Author: M. Graille
Author: E.A. Stura
Author: N.G. Housden
Author: S.P. Bottomley
Author: D. Beale
Author: M.J. Taussig
Author: B.J. Sutton
Author: M.G. Gore
Author: J.-B. Charbonnier

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