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The Moraxella catarrhalis outer membrane protein CD contains two distinct domains specifying adherence to human lung

Christine Akimana1, Eric R Lafontaine

  • 1Department of Medical Microbiology and Immunology, University of Toledo Health Sciences Campus, Toledo, OH, USA.

FEMS Microbiology Letters
|March 30, 2007
PubMed

Insights

Moraxella catarrhalis outer membrane protein (OMPCD) has two binding domains crucial for adhering to human lung cells. These domains, including a thrombospondin-type 3 repeat motif, mediate bacterial attachment.

Area of Science:

  • Microbiology
  • Cell Biology
  • Protein Structure-Function

Background:

  • Moraxella catarrhalis is a common human respiratory pathogen.
  • The outer membrane protein OMPCD (453 residues) is conserved among M. catarrhalis isolates.
  • OMPCD mediates bacterial binding to A549 human lung cells.

Purpose of the Study:

  • To identify the specific domains of M. catarrhalis OMPCD responsible for adherence to human lung cells.
  • To characterize the adhesive properties of OMPCD domains.

Main Methods:

  • Expression of truncated OMPCD proteins in Escherichia coli.
  • Cellular enzyme-linked immunosorbent assays (ELISA) with His-tagged proteins.
  • Database searches for conserved motifs.
  • Construction of a surface-display system using M. catarrhalis autotransporter McaP.

Main Results:

  • Two distinct domains within OMPCD (residues 1-240 and 241-400) are important for A549 cell attachment.
  • A thrombospondin-type 3 repeat (TT3R) motif (amino acids 285-299) within OMPCD contributes to adhesion.
  • Residues 236-300 of OMPCD exhibit adhesive properties.
  • Purified OMPCD (residues 16-236) binds to A549 cells.
  • The two cell-binding domains were further refined to amino acids 16-150 and 261-300 using a surface-display system.

Conclusions:

  • OMPCD possesses at least two distinct cell-binding domains that mediate M. catarrhalis adherence to human lung cells.
  • The TT3R motif is a key component of one of these adhesive domains.
  • Understanding OMPCD's adhesive domains provides insights into M. catarrhalis pathogenesis and potential therapeutic targets.

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