title: A holin and an endopeptidase are essential for chitinolytic protein secretion in Serratia marcescens.
abstract: 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.
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Jaeger J
authors.initials: JJ
authors.lastname: Hamilton
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Marlow
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Owen
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Marília de Assis Alcoforado
authors.initials: Mde A
authors.lastname: Costa
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Manman
authors.initials: M
authors.lastname: Guo
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Grant
authors.initials: G
authors.lastname: Buchanan
authors.affiliation: Department of Molecular Microbiology, John Innes Centre, Norwich NR4 7TJ, England, UK.
authors.forename: Govind
authors.initials: G
authors.lastname: Chandra
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Matthias
authors.initials: M
authors.lastname: Trost
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Coulthurst
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Tracy
authors.initials: T
authors.lastname: Palmer
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Nicola R
authors.initials: NR
authors.lastname: Stanley-Wall
authors.affiliation: Division of Molecular Microbiology and Medical Research Council Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK f.sargent@dundee.ac.uk.
authors.forename: Frank
authors.initials: F
authors.lastname: Sargent
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002688:Chitinases / Q000235:genetics / Q000378:metabolism*; D010450:Endopeptidases / Q000502:physiology*; D005798:Genes, Bacterial; D056426:Genetic Loci; D021381:Protein Transport; D012706:Serratia marcescens / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002688:Chitinases; D010450:Endopeptidases