title: Novel oligosaccharide side chains of the collagen-like region of BclA, the major glycoprotein of the Bacillus anthracis exosporium.
abstract: Spores of Bacillus anthracis, the causative agent of anthrax, are enclosed by a prominent loose fitting layer called the exosporium. The exosporium consists of a basal layer and an external hairlike nap. The filaments of the nap are composed of a highly immunogenic glycoprotein called BclA, which has a long, central collagen-like region with multiple XXG repeats. Most of the triplet repeats are PTG, and nearly all of the triplet repeats contain a threonine residue, providing multiple potential sites for O-glycosylation. In this study, we demonstrated that two O-linked oligosaccharides, a 715-Da tetrasaccharide and a 324-Da disaccharide, are released from spore- and exosporium-associated BclA by hydrazinolysis. Each oligosaccharide is probably attached to BclA through a GalNAc linker, which was lost during oligosaccharide release. We found that multiple copies of the tetrasaccharide are linked to the collagen-like region of BclA, whereas the disaccharide may be attached outside of this region. Using NMR, mass spectrometry, and other analytical techniques, we determined that the structure of the tetrasaccharide is 2-O-methyl-4-(3-hydroxy-3-methylbutamido)-4,6-dideoxy-beta-d-glucopyranosyl-(1-->3)-alpha-l-rhamnopyranosyl-(1-->3)-alpha-l-rhamnopyranosyl-(1-->2)-l-rhamnopyranose. The previously undescribed nonreducing terminal sugar (i.e. 2-O-methyl-4-(3-hydroxy-3-methylbutamido)-4,6-dideoxy-d-glucose) was given the trivial name anthrose. Anthrose was not found in spores of either Bacillus cereus or Bacillus thuringiensis, two species that are the most phylogenetically similar to B. anthracis. Thus, anthrose may be useful for species-specific detection of B. anthracis spores or as a new target for therapeutic intervention.
authors.affiliation: Department of Microbiology, Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Daubenspeck
authors.forename: Huadong
authors.initials: H
authors.lastname: Zeng
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
authors.forename: Shengli
authors.initials: S
authors.lastname: Dong
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Steichen
authors.forename: N Rama
authors.initials: NR
authors.lastname: Krishna
authors.forename: David G
authors.initials: DG
authors.lastname: Pritchard
authors.forename: Charles L
authors.initials: CL
authors.lastname: Turnbough
mesh_terms: D001408:Bacillus anthracis / Q000737:chemistry* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001483:Base Sequence; D002240:Carbohydrate Sequence; D003094:Collagen / Q000737:chemistry; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D009844:Oligosaccharides / Q000737:chemistry / Q000235:genetics; D012210:Rhamnose / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013171:Spores, Bacterial / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; C470593:BclA protein, Bacillus anthracis; D004269:DNA, Bacterial; D008562:Membrane Glycoproteins; D009844:Oligosaccharides; D003094:Collagen; D012210:Rhamnose