A pseudaminic acid or a legionaminic acid derivative transferase is strain-specifically implicated in the general protein O-glycosylation system of the periodontal pathogen Tannerella forsythia.
The occurrence of nonulosonic acids in bacteria is wide-spread and linked to pathogenicity. However, the knowledge of cognate nonulosonic acid transferases is scarce. In the periodontopathogen Tannerella forsythia, several proposed virulence factors carry strain-specifically either a pseudaminic or a legionaminic acid derivative as terminal sugar on an otherwise structurally identical, protein-bound oligosaccharide. This study aims to shed light on the transfer of either nonulosonic acid derivative on a proximal N-acetylmannosaminuronic acid residue within the O-glycan structure, exemplified with the bacterium's abundant S-layer glycoproteins. Bioinformatic analyses provided the candidate genes Tanf_01245 (strain ATCC 43037) and TFUB4_00887 (strain UB4), encoding a putative pseudaminic and a legionaminic acid derivative transferase, respectively. These transferases have identical C-termini and contain motifs typical of glycosyltransferases (DXD) and bacterial sialyltransferases (D/E-D/E-G and HP). They share homology to type B glycosyltransferases and TagB, an enzyme catalyzing glycerol transfer to an N-acetylmannosamine residue in teichoic acid biosynthesis. Analysis of a cellular pool of nucleotide-activated sugars confirmed the presence of the CMP-activated nonulosonic acid derivatives, which are most likely serving as substrates for the corresponding transferase. Single gene knock-out mutants targeted at either transferase were analyzed for S-layer O-glycan composition by ESI-MS, confirming the loss of the nonulosonic acid derivative. Cross-complementation of the mutants with the nonnative nonulosonic acid transferase was not successful indicating high stringency of the enzymes. This study identified plausible candidates for a pseudaminic and a legionaminic acid derivative transferase; these may serve as valuable tools for engineering of novel sialoglycoconjugates.
Department of NanoBiotechnology, NanoGlycobiology Unit, Universität für Bodenkultur Wien, Muthgasse 11, A-1190 Vienna, Austria.
Markus B
MB
Tomek
Department of NanoBiotechnology, NanoGlycobiology Unit, Universität für Bodenkultur Wien, Muthgasse 11, A-1190 Vienna, Austria.
Bettina
B
Janesch
Department of Chemistry, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Vienna, Austria.
Daniel
D
Maresch
Department of Chemistry, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Vienna, Austria.
Markus
M
Windwarder
Department of Chemistry, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Vienna, Austria.
Friedrich
F
Altmann
Department of NanoBiotechnology, NanoGlycobiology Unit, Universität für Bodenkultur Wien, Muthgasse 11, A-1190 Vienna, Austria.
Paul
P
Messner
Department of NanoBiotechnology, NanoGlycobiology Unit, Universität für Bodenkultur Wien, Muthgasse 11, A-1190 Vienna, Austria.
Christina
C
Schäffer
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D009154:Mutation; D017386:Sequence Homology, Amino Acid; D012794:Sialic Acids / Q000737:chemistry / Q000378:metabolism*; D012799:Sialyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000070436:Tannerella forsythia / Q000201:enzymology*
C110570:5,7-diacetamido-8-O-acetyl-3,5,7,9-tetradeoxy-glycero-talo-nonulosonic acid; D001426:Bacterial Proteins; D012794:Sialic Acids; D012799:Sialyltransferases
Bacteroidetes; glycoengineering; glycosyltransferase; nonulosonic acids; periodontitis