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The Escherichia coli amidase AmiC is a periplasmic septal ring component exported via the twin-arginine transport

Thomas G Bernhardt1, Piet A J de Boer

  • 1Case Western Reserve University, School of Medicine, Department of Molecular Biology and Microbiology, W239, 10900 Euclid Ave., Cleveland, OH 44106, USA.

Molecular Microbiology
|June 6, 2003
PubMed

Insights

Escherichia coli amidases AmiA and AmiC are transported to the periplasm via the twin-arginine (Tat) pathway, explaining Tat-deficient cell division defects. AmiC specifically localizes to the septal ring, a novel finding for periplasmic proteins.

Area of Science:

  • Microbiology
  • Cell Biology
  • Protein Transport

Background:

  • N-acetylmuramoyl-l-alanine amidases (AmiA, AmiB, AmiC) in Escherichia coli are periplasmic enzymes crucial for murein cross-link degradation during cell division.
  • Defects in amidase function or the twin-arginine protein transport (Tat) pathway lead to cell chaining, indicating a shared role in cell division.
  • The precise localization and transport mechanisms of these amidases remain incompletely understood.

Purpose of the Study:

  • To investigate the role of the Tat pathway in the periplasmic localization of AmiA and AmiC.
  • To determine the sub-cellular localization of AmiA and AmiC during cell division.
  • To elucidate the mechanism of AmiC recruitment to the septal ring.

Main Methods:

  • Utilizing functional fusions of AmiA and AmiC with green fluorescent protein (GFP) to track their localization in live Escherichia coli cells.
  • Leveraging the Tat pathway's ability to export prefolded GFP to the periplasm.
  • Investigating the role of FtsN in the recruitment of AmiC to the septal ring.

Main Results:

  • Both AmiA and AmiC are confirmed to be transported to the periplasm via the Tat pathway.
  • AmiA-GFP is dispersed throughout the periplasm.
  • AmiC-GFP localizes to the septal ring in constricting cells, mediated by an N-terminal domain and dependent on FtsN.

Conclusions:

  • The Tat pathway is essential for the periplasmic localization of AmiA and AmiC, explaining the division defects observed in Tat-deficient cells.
  • AmiC is a novel, periplasmic component recruited to the septal ring, dependent on FtsN, and represents the latest known recruit to this division structure.

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