title: Disruption of Mycobacterial AftB Results in Complete Loss of Terminal β(1 → 2) Arabinofuranose Residues of Lipoarabinomannan.
abstract: Lipoarabinomannan (LAM) and arabinogalactan (AG) are the two major mycobacterial cell wall (lipo)polysaccharides, which contain a structurally similar arabinan domain that is highly branched and assembled in a stepwise fashion by variety of arabinofuranosyltransferases (ArafT). In addition to playing an essential role in mycobacterial physiology, LAM and its biochemical precursor lipomannan possess potent immunomodulatory activities that affect the host immune response. In the search of additional mycobacterial ArafTs that participate in the synthesis of the arabinan segment of LAM, we disrupted aftB (MSMEG_6400) in Mycobacterium smegmatis. The deletion of chromosomal aftB locus could only be achieved in the presence of a rescue plasmid carrying a functional copy of aftB, strongly suggesting that it is essential for the viability of M. smegmatis. Isolation and detailed structural characterization of a LAM molecule derived from the conditional mutant deficient in AftB revealed the absence of terminal β(1 → 2)-linked arabinofuranosyl residues. Furthermore, we demonstrated that truncated LAM displays proinflammatory activity, which is due to its ability to activate Toll-like receptor 2. All together, our results indicate that AftB is an essential mycobacterial ArafT that plays a role in the synthesis of the arabinan domain of LAM.
authors.affiliation: School of Biosciences, Institute of Microbiology and Infection, University of Birmingham , Edgbaston, B15 2TT Birmingham, United Kingdom.
authors.forename: Monika
authors.initials: M
authors.lastname: Jankute
authors.affiliation: School of Biosciences, Institute of Microbiology and Infection, University of Birmingham , Edgbaston, B15 2TT Birmingham, United Kingdom.
authors.forename: Luke J
authors.initials: LJ
authors.lastname: Alderwick
authors.affiliation: Institute of Bio- and Geosciences, IBG-1: Biotechnology, Forschungszentrum Jülich GmbH , Jülich D-52425, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Noack
authors.affiliation: School of Biosciences, Institute of Microbiology and Infection, University of Birmingham , Edgbaston, B15 2TT Birmingham, United Kingdom.
authors.forename: Natacha
authors.initials: N
authors.lastname: Veerapen
authors.affiliation: Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, UPS , 31077 Toulouse, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Nigou
authors.affiliation: School of Biosciences, Institute of Microbiology and Infection, University of Birmingham , Edgbaston, B15 2TT Birmingham, United Kingdom.
authors.forename: Gurdyal S
authors.identifier: 0000-0002-5605-0395
authors.initials: GS
authors.lastname: Besra
mesh_terms: D001089:Arabinose / Q000031:analogs & derivatives* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis; D015870:Gene Expression; D006801:Humans; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D016207:Cytokines; D008070:Lipopolysaccharides; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; C431714:arabinofuranose; C050016:lipoarabinomannan; D001089:Arabinose