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Streptococcus pneumoniae PBP2x mid-cell localization requires the C-terminal PASTA domains and is essential for cell

Katharina Peters1, Inga Schweizer, Katrin Beilharz

  • 1Department of Microbiology, University of Kaiserslautern, Paul-Ehrlich Straße 23, D-67663, Kaiserslautern, Germany.

Molecular Microbiology
|March 25, 2014
PubMed

Insights

Penicillin-binding protein 2x (PBP2x) is essential for Streptococcus pneumoniae cell division. Its localization to the cell septum is independent of its transpeptidase activity, requiring PASTA domains and influenced by HtrA.

Area of Science:

  • Microbiology
  • Cell Biology
  • Molecular Biology

Background:

  • Penicillin-binding protein 2x (PBP2x) is crucial for murein biosynthesis and cell division in Streptococcus pneumoniae.
  • Understanding PBP2x localization is key to elucidating its role in bacterial cell division.

Purpose of the Study:

  • To investigate the molecular mechanisms governing the localization of PBP2x in live Streptococcus pneumoniae cells.
  • To determine the functional domains of PBP2x required for its proper localization and activity.

Main Methods:

  • Construction of N-terminal GFP-PBP2x fusions under a zinc-inducible promoter.
  • Live-cell imaging to observe PBP2x localization.
  • Functional assays including protein depletion and genetic inactivation.
  • Analysis of PBP2x derivatives with deletions in key domains.

Main Results:

  • Functional GFP-PBP2x fusions localized to mid-cell and supported growth in the absence of endogenous PBP2x.
  • PBP2x depletion caused severe morphological defects, confirming its essentiality for cell division.
  • Inactive or domain-deleted PBP2x variants localized correctly, indicating localization is independent of transpeptidase activity.
  • Localization requires PASTA domains and is affected by the protease/chaperone HtrA.
  • PBP2x localizes to the septum, similar to PBP1a and StkP, positioning it within the divisome complex.

Conclusions:

  • PBP2x localization to the Streptococcus pneumoniae cell division site is independent of its catalytic transpeptidase activity.
  • The C-terminal PASTA domains are critical for PBP2x localization, with HtrA identified as a targeting factor.
  • PBP2x is a vital component of the bacterial divisome, essential for cell division.

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