4NBX

Crystal Structure of Clostridium difficile Toxin A fragment TcdA-A1 Bound to A20.1 VHH

Summary for 4NBX

• Entry DOI: 10.2210/pdb4nbx/pdb
• Related: 2F6E 2G7C 4NBY 4NBZ 4NC0 4NC1 4NC2
• Descriptor: TcdA, A20.1 VHH (3 entities in total)
• Functional Keywords: antibody-antigen complex, immune system
• Biological source: Clostridium difficile; More
• Total number of polymer chains: 2
• Total formula weight: 32985.44

Authors

Murase, T.,Eugenio, L.,Schorr, M.,Hussack, G.,Tanha, J.,Kitova, E.N.,Klassen, J.S.,Ng, K.K.S. (deposition date: 2013-10-23, release date: 2013-12-11, Last modification date: 2014-02-12)

Primary citation

Murase, T.,Eugenio, L.,Schorr, M.,Hussack, G.,Tanha, J.,Kitova, E.N.,Klassen, J.S.,Ng, K.K.
Structural Basis for Antibody Recognition in the Receptor-binding Domains of Toxins A and B from Clostridium difficile.
J.Biol.Chem., 289:2331-2343, 2014

PubMed Abstract: Clostridium difficile infection is a serious and highly prevalent nosocomial disease in which the two large, Rho-glucosylating toxins TcdA and TcdB are the main virulence factors. We report for the first time crystal structures revealing how neutralizing and non-neutralizing single-domain antibodies (sdAbs) recognize the receptor-binding domains (RBDs) of TcdA and TcdB. Surprisingly, the complexes formed by two neutralizing antibodies recognizing TcdA do not show direct interference with the previously identified carbohydrate-binding sites, suggesting that neutralization of toxin activity may be mediated by mechanisms distinct from steric blockage of receptor binding. A camelid sdAb complex also reveals the molecular structure of the TcdB RBD for the first time, facilitating the crystallization of a strongly negatively charged protein fragment that has resisted previous attempts at crystallization and structure determination. Electrospray ionization mass spectrometry measurements confirm the stoichiometries of sdAbs observed in the crystal structures. These studies indicate how key epitopes in the RBDs from TcdA and TcdB are recognized by sdAbs, providing molecular insights into toxin structure and function and providing for the first time a basis for the design of highly specific toxin-specific therapeutic and diagnostic agents.

PubMed: 24311789
DOI: 10.1074/jbc.M113.505917

Experimental method

X-RAY DIFFRACTION (1.75 Å)