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

Jaeger J. Hamilton, Victoria L. Marlow, Richard A. Owen, Marília de Assis Alcoforado Costa, Manman Guo, Grant Buchanan, Govind Chandra, Matthias Trost, Sarah J. Coulthurst, Tracy Palmer, Nicola R. Stanley-Wall, Frank Sargent (Lead / Corresponding author)

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Pathogenic bacteria adapt to their environment and manipulate the biochemistry of hosts by secretion of effector molecules. Serratia marcescens is an opportunistic pathogen associated with healthcare-acquired infections and is a prolific secretor of proteins, including three chitinases (ChiA, ChiB, and ChiC) and a chitin binding protein (Cbp21). In this work, genetic, biochemical, and proteomic approaches identified genes that were required for secretion of all three chitinases and Cbp21. A genetic screen identified a holin-like protein (ChiW) and a putative l-alanyl-d-glutamate endopeptidase (ChiX), and subsequent biochemical analyses established that both were required for nonlytic secretion of the entire chitinolytic machinery, with chitinase secretion being blocked at a late stage in the mutants. In addition, live-cell imaging experiments demonstrated bimodal and coordinated expression of chiX and chiA and revealed that cells expressing chiA remained viable. It is proposed that ChiW and ChiX operate in tandem as components of a protein secretion system used by gram-negative bacteria.

Original languageEnglish
Pages (from-to)615-626
Number of pages12
JournalJournal of Cell Biology
Issue number5
Publication statusPublished - 8 Dec 2014


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