Article

Conserved patterns hidden within group A Streptococcus M protein hypervariability recognize human C4b-binding protein

  • Nature Microbiology 1, Article number: 16155 (2016)
  • doi:10.1038/nmicrobiol.2016.155
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Abstract

No vaccine exists against group A Streptococcus (GAS), a leading cause of worldwide morbidity and mortality. A severe hurdle is the hypervariability of its major antigen, the M protein, with >200 different M types known. Neutralizing antibodies typically recognize M protein hypervariable regions (HVRs) and confer narrow protection. In stark contrast, human C4b-binding protein (C4BP), which is recruited to the GAS surface to block phagocytic killing, interacts with a remarkably large number of M protein HVRs (apparently 90%). Such broad recognition is rare, and we discovered a unique mechanism for this through the structure determination of four sequence-diverse M proteins in complexes with C4BP. The structures revealed a uniform and tolerant ‘reading head’ in C4BP, which detected conserved sequence patterns hidden within hypervariability. Our results open up possibilities for rational therapies that target the M–C4BP interaction, and also inform a path towards vaccine design.

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Acknowledgements

We thank O. Ghosh for help on the project. This works was supported by National Institutes of Health (NIH) grant T32 GM007240 (C.Z.B.), American Heart Association Predoctoral Fellowship 14PRE18320032 (C.Z.B.), NIH R01 AI096837 (P.G. and V.N.) and NIH R01 AI077780 (V.N.). The work was also funded in part by the National Biomedical Computation Resource, NIH P41 GM103426, NIH Director's New Innovator Award Program DP2-OD007237 and through the National Science Foundation XSEDE Supercomputer Resources Grant RAC CHE060073N to R.E.A. S.P.H. was supported by the Interfaces Multi-Scale Analysis of Biological Structure and Function training grant NIH T32 EB009380.

Author information

Affiliations

  1. Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, California 92093, USA

    • Cosmo Z. Buffalo
    • , Adrian J. Bahn-Suh
    • , Sophia P. Hirakis
    • , Tapan Biswas
    • , Rommie E. Amaro
    •  & Partho Ghosh
  2. Department of Pediatrics, University of California, San Diego, La Jolla, California 92093, USA

    • Victor Nizet
  3. Skaggs School of Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093, USA

    • Victor Nizet

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Contributions

C.Z.B., V.N. and P.G. conceived the experiments. C.Z.B., A.J.B.-S. and T.B. carried out the structure determinations. C.Z.B. and A.J.B.-S. carried out the binding studies. S.P.H. and R.E.A. carried out and analysed the MD simulations. C.Z.B. and P.G. wrote the paper with input from all the authors.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Partho Ghosh.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    Supplementary Tables 1–3, Supplementary Figures 1–16, legends for Supplementary Videos 1–5, Supplementary References

Videos

  1. 1.

    Supplementary Video 1

    R39 nook in M2-C4BPα1-2.

  2. 2.

    Supplementary Video 2

    R39 nook in M2 (F75A)-C4BPα1-2.

  3. 3.

    Supplementary Video 3

    C4BPα2 contacts in M2-C4BPα1-2.

  4. 4.

    Supplementary Video 4

    C4BPα2 contacts in M2 (K65A)-C4BPα1-2.

  5. 5.

    Supplementary Video 5

    C4BPα2 contacts in M2 (N66D)-C4BPα1-2.