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Assays for Studying the Role of Vitronectin in Bacterial Adhesion and Serum Resistance
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Assays for Studying the Role of Vitronectin in Bacterial Adhesion and Serum Resistance

Published on: October 16, 2018

Haemophilus influenzae protein E recognizes the C-terminal domain of vitronectin and modulates the membrane attack

Birendra Singh1, Farshid Jalalvand, Matthias Mörgelin

  • 1Medical Microbiology and Medical Protein Chemistry, Department of Laboratory Medicine Malmö, Lund University, Skåne University Hospital, SE-205 02 Malmö, Sweden.

Molecular Microbiology
|May 6, 2011
PubMed

Insights

Haemophilus influenzae protein E (PE) binds vitronectin (Vn), preventing complement-mediated bacterial killing. Mutating key residues in PE enhances bacterial susceptibility to the membrane attack complex (MAC), revealing a novel immune evasion mechanism.

Area of Science:

  • Microbiology
  • Immunology
  • Molecular Biology

Background:

  • Haemophilus influenzae protein E (PE) is an adhesin that triggers inflammation.
  • PE binds vitronectin (Vn), inhibiting complement-mediated bacterial killing by blocking membrane attack complex (MAC) formation.

Purpose of the Study:

  • To characterize the interaction between H. influenzae PE and Vn.
  • To identify the specific residues and domains involved in PE-Vn binding.
  • To elucidate the role of this interaction in bacterial complement evasion.

Main Methods:

  • Site-directed mutagenesis of PE.
  • Production of soluble and surface-expressed PE variants in E. coli.
  • Analysis of Vn binding using truncated Vn molecules.
  • Assessment of bactericidal activity and MAC deposition in human serum.

Main Results:

  • Residues K85 and R86 in PE are crucial for Vn binding.
  • PE binding to Vn effectively quenches Vn's function.
  • The C-terminal domain of Vn (Vn353-363) is the primary binding site for PE.
  • Mutants lacking PE or with altered Vn-binding capacity showed increased MAC deposition.

Conclusions:

  • H. influenzae PE employs a finely tuned mechanism to evade the innate immune system.
  • PE's interaction with Vn is critical for inhibiting complement deposition and MAC formation.
  • Targeting the PE-Vn interaction could be a strategy to enhance bacterial clearance.

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