title: Lcp1 Is a Phosphotransferase Responsible for Ligating Arabinogalactan to Peptidoglycan in Mycobacterium tuberculosis.
abstract: Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), has a unique cell envelope which accounts for its unusual low permeability and contributes to resistance against common antibiotics. The main structural elements of the cell wall consist of a cross-linked network of peptidoglycan (PG) in which some of the muramic acid residues are covalently attached to a complex polysaccharide, arabinogalactan (AG), via a unique α-l-rhamnopyranose-(1→3)-α-d-GlcNAc-(1→P) linker unit. While the molecular genetics associated with PG and AG biosynthetic pathways have been largely delineated, the mechanism by which these two major pathways converge has remained elusive. In Gram-positive organisms, the LytR-CpsA-Psr (LCP) family of proteins are responsible for ligating cell wall teichoic acids to peptidoglycan, through a linker unit that bears a striking resemblance to that found in mycobacterial arabinogalactan. In this study, we have identified Rv3267 as a mycobacterial LCP homolog gene that encodes a phosphotransferase which we have named Lcp1. We demonstrate that lcp1 is an essential gene required for cell viability and show that recombinant Lcp1 is capable of ligating AG to PG in a cell-free radiolabeling assay.
  
  
  
  Tuberculosis is an infectious disease caused by the bacterial organism Mycobacterium tuberculosis Survival of M. tuberculosis rests critically on the integrity of its unique cell wall; therefore, a better understanding of how the genes and enzymes involved in cell wall assembly work is fundamental for us to develop new drugs to treat this disease. In this study, we have identified Lcp1 as an essential phosphotransferase that ligates together arabinogalactan and peptidoglycan, two crucial cell wall macromolecules found within the mycobacterial cell wall. The discovery of Lcp1 sheds new light on the final stages of mycobacterial cell wall assembly and represents a key biosynthetic step that could be exploited for new anti-TB drug discovery.
authors.affiliation: Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: James
authors.initials: J
authors.lastname: Harrison
authors.affiliation: Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Georgina
authors.initials: G
authors.lastname: Lloyd
authors.affiliation: Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Gunning-Lemieux Chemistry Centre, Edmonton, Canada.
authors.forename: Maju
authors.initials: M
authors.lastname: Joe
authors.affiliation: Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Gunning-Lemieux Chemistry Centre, Edmonton, Canada.
authors.forename: Todd L
authors.initials: TL
authors.lastname: Lowary
authors.affiliation: Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Edward
authors.initials: E
authors.lastname: Reynolds
authors.affiliation: Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Hannah
authors.initials: H
authors.lastname: Walters-Morgan
authors.affiliation: Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Apoorva
authors.initials: A
authors.lastname: Bhatt
authors.affiliation: Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Andrew
authors.initials: A
authors.lastname: Lovering
authors.affiliation: Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Gurdyal S
authors.initials: GS
authors.lastname: Besra
authors.affiliation: Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom l.alderwick@bham.ac.uk.
authors.forename: Luke J
authors.initials: LJ
authors.lastname: Alderwick
mesh_terms: D005685:Galactans / Q000378:metabolism*; D020043:Genes, Essential; D050296:Microbial Viability; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D010457:Peptidoglycan / Q000378:metabolism*; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism*
chemical_list: D005685:Galactans; D010457:Peptidoglycan; D010770:Phosphotransferases; C005653:arabinogalactan