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Measurement of Chitinase Activity in Biological Samples
03:32

Measurement of Chitinase Activity in Biological Samples

Published on: August 22, 2019

11.0K

A holin and an endopeptidase are essential for chitinolytic protein secretion in Serratia marcescens

Jaeger J Hamilton1, Victoria L Marlow1, Richard A Owen1

  • 1Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.

The Journal of Cell Biology
|December 10, 2014
PubMed

Insights

Serratia marcescens utilizes a novel secretion system involving ChiW and ChiX proteins. These components are essential for releasing chitinases and Cbp21, crucial for the opportunistic pathogen

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Protein Secretion

Background:

  • Serratia marcescens is an opportunistic pathogen causing healthcare-associated infections.
  • Pathogenic bacteria secrete effector molecules to adapt and manipulate host biochemistry.
  • S. marcescens secretes chitinases (ChiA, ChiB, ChiC) and a chitin-binding protein (Cbp21).

Purpose of the Study:

  • To identify genes essential for the secretion of S. marcescens chitinolytic machinery.
  • To elucidate the mechanism of nonlytic secretion of chitinases and Cbp21.

Main Methods:

  • Genetic screening to identify novel secretion genes.
  • Biochemical analyses to confirm protein function.
  • Proteomic approaches to analyze secreted proteins.
  • Live-cell imaging to study gene expression and cell viability.

Main Results:

  • A holin-like protein (ChiW) and an endopeptidase (ChiX) were identified as essential for secretion.
  • ChiW and ChiX are required for the nonlytic secretion of ChiA, ChiB, ChiC, and Cbp21.
  • Secretion was blocked at a late stage in chiW and chiX mutants.
  • Bimodal and coordinated expression of chiX and chiA was observed, with chiA-expressing cells remaining viable.

Conclusions:

  • ChiW and ChiX function together in a novel protein secretion system in S. marcescens.
  • This system facilitates the nonlytic release of the chitinolytic machinery.
  • The findings provide insights into protein secretion mechanisms in Gram-negative bacteria.

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