Title

Crystal structure of Streptococcus pyogenes EndoS, an immunomodulatory endoglycosidase specific for human IgG antibodies

UMMS Affiliation

Program in Bioinformatics and Integrative Biology; Department of Biochemistry and Molecular Pharmacology

Date

5-6-2014

Document Type

Article

Medical Subject Headings

Bacterial Proteins; Catalytic Domain; Crystallography, X-Ray; Glycoside Hydrolases; Humans; Immunoglobulin Fc Fragments; Immunoglobulin G; Immunologic Factors; Models, Molecular; Protein Conformation; Protein Structure, Tertiary; Scattering, Small Angle; Streptococcus pyogenes; Substrate Specificity; X-Ray Diffraction

Disciplines

Biochemistry, Biophysics, and Structural Biology | Bioinformatics | Computational Biology | Integrative Biology | Systems Biology

Abstract

To evade host immune mechanisms, many bacteria secrete immunomodulatory enzymes. Streptococcus pyogenes, one of the most common human pathogens, secretes a large endoglycosidase, EndoS, which removes carbohydrates in a highly specific manner from IgG antibodies. This modification renders antibodies incapable of eliciting host effector functions through either complement or Fc gamma receptors, providing the bacteria with a survival advantage. On account of this antibody-specific modifying activity, EndoS is being developed as a promising injectable therapeutic for autoimmune diseases that rely on autoantibodies. Additionally, EndoS is a key enzyme used in the chemoenzymatic synthesis of homogenously glycosylated antibodies with tailored Fc gamma receptor-mediated effector functions. Despite the tremendous utility of this enzyme, the molecular basis of EndoS specificity for, and processing of, IgG antibodies has remained poorly understood. Here, we report the X-ray crystal structure of EndoS and provide a model of its encounter complex with its substrate, the IgG1 Fc domain. We show that EndoS is composed of five distinct protein domains, including glycosidase, leucine-rich repeat, hybrid Ig, carbohydrate binding module, and three-helix bundle domains, arranged in a distinctive V-shaped conformation. Our data suggest that the substrate enters the concave interior of the enzyme structure, is held in place by the carbohydrate binding module, and that concerted conformational changes in both enzyme and substrate are required for subsequent antibody deglycosylation. The EndoS structure presented here provides a framework from which novel endoglycosidases could be engineered for additional clinical and biotechnological applications.

Rights and Permissions

Citation: Proc Natl Acad Sci U S A. 2014 May 6;111(18):6714-9. doi: 10.1073/pnas.1322908111. Epub 2014 Apr 21. Link to article on publisher's site

Related Resources

Link to Article in PubMed