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Haemophilus influenzae surface fibril (Hsf) is a unique twisted hairpin-like trimeric autotransporter

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Author

Summary, in English

The Haemophilus surface fibril (Hsf) is an extraordinary large (2413 amino acids) trimeric autotransporter, present in all encapsulated Haemophilus influenzae. It contributes to virulence by directly functioning as an adhesin. Furthermore, Hsf recruits the host factor vitronectin thereby inhibiting the host innate immune response resulting in enhanced survival in serum. Here we observed by electron microscopy that Hsf appears as an 100. nm long fibril at the bacterial surface albeit the length is approximately 200. nm according to a bioinformatics based model. To unveil this discrepancy, we denaturated Hsf at the surface of Hib by using guanidine hydrochloride (GuHCl). Partial denaturation induced in the presence of GuHCl unfolded the Hsf molecules, and resulted in an increased length of fibres in comparison to the native trimeric form. Importantly, our findings were also verified by E. coli expressing Hsf at its surface. In addition, a set of Hsf-specific peptide antibodies also indicated that the N-terminal of Hsf is located near the C-terminal at the base of the fibril. Taken together, our results demonstrated that Hsf is not a straight molecule but is folded and doubled over. This is the first report that provides the unique structural features of the trimeric autotransporter Hsf.

Publishing year

2015

Language

English

Pages

27-37

Publication/Series

International Journal of Medical Microbiology

Volume

305

Issue

1

Document type

Journal article

Publisher

Elsevier

Topic

  • Microbiology in the medical area

Keywords

  • Haemophilus influenzae type b
  • Haemophilus surface fibril
  • Hib
  • Hsf

Status

Published

Research group

  • Medical Microbiology

ISBN/ISSN/Other

  • ISSN: 1618-0607