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The single-domain response regulator LerC functions as a connector protein in the Legionella pneumophila effectors

Yaron S Feldheim1, Tal Zusman1, Anya Kapach1

  • 1Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, Israel.

Molecular Microbiology
|August 15, 2018
PubMed

Insights

Legionella pneumophila uses a new connector protein, LerC, to link two regulatory systems. LerC bridges the PmrAB and LetAS two-component systems (TCSs), controlling effector protein secretion during infection.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Legionella pneumophila injects over 300 effector proteins into host cells.
  • Two-component systems (TCSs), PmrAB and LetAS, regulate effector-encoding genes (EEGs).
  • PmrAB activates EEGs, while LetAS, via the LetAS-RsmYZ-CsrA cascade, represses EEGs.

Purpose of the Study:

  • To identify regulatory proteins connecting the PmrAB and LetAS TCSs.
  • To elucidate the function of a novel single-domain response regulator (SDRR) in Legionella pneumophila.
  • To understand the mechanism by which LerC modulates EEG expression.

Main Methods:

  • Genetic analysis to identify the lerC gene.
  • Biochemical assays to study LerC protein interaction with LetS.
  • Phosphorylation assays to determine LerC's functional requirements.
  • Gene expression analysis to assess the impact of LerC on EEGs.

Main Results:

  • A novel SDRR, LerC, was identified as a connector protein between PmrAB and LetAS TCSs.
  • PmrAB TCS activates lerC gene expression, and LerC protein inhibits LetAS TCS activity.
  • LerC interacts with LetS's histidine-phosphotransfer domain, reducing RsmY and RsmZ small RNA expression.
  • Phosphorylation of LerC's receiver domain is crucial for its function, acting as a phosphate sink for LetS.

Conclusions:

  • LerC acts as a crucial link between PmrAB and LetAS TCSs, fine-tuning effector protein secretion.
  • This study reveals a novel function for SDRRs as connector proteins within bacterial regulatory networks.
  • The findings suggest that SDRRs may play similar connector roles in other bacterial regulatory systems.

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