Identification of a gene involved in the biosynthesis pathway of the terminal sugar of the archaellin N-linked tetrasaccharide in Methanococcus maripaludis

Abstract

In Methanococcus maripaludis, the three archaellins which comprise the archaellum are modified at multiple sites with an N-linked tetrasaccharide with the structure of Sug-4-β-ManNAc3NAmA6Thr-4-β-GlcNAc3NAcA-3-β-GalNAc, where Sug is a unique sugar (5S)-2-acetamido-2,4-dideoxy-5-O-methyl-L-erythro-hexos-5-ulo-1,5-pyranose, so far found exclusively in this species. In this study, a six-gene cluster mmp1089-1094, neighboring one of the genomic regions already known to contain genes involved with the archaellin N-glycosylation pathway, was examined for its potential involvement in the archaellin N-glycosylation or sugar biosynthesis pathway. The co-transcription of these six genes was demonstrated by RT-PCR. Mutants carrying an in-frame deletion in mmp1090, mmp1091 or mmp1092 were successfully generated. The Δmmp1090 deletion mutant was archaellated when examined by electron microscopy and mass spectrometry analysis of purified archaella showed that the archaellins were modified with a truncated N-glycan in which the terminal sugar residue and the threonine linked to the third sugar residue were missing. Both gene annotation and bioinformatic analyses indicate that MMP1090 is a UDP-glucose 4-epimerase, suggesting that the unique terminal sugar of the archaellin N-glycan might be synthesised from UDP-glucose or UDP-N-acetylglucosamine with an essential early step in synthesis catalysed by MMP1090. In contrast, no detectable phenotype related to archaellin glycosylation was observed in mutants deleted for either mmp1091 or mmp1092 while attempts to delete mmp1089, mmp1093 and mmp1094 were unsuccessful. Based on its demonstrated involvement in the archaellin N-glycosylation pathway, we designated mmp1090 as aglW.

Emerging facets of prokaryotic glycosylation

“…This study included a rare example of an archaeal gene functionally replacing a bacterial gene in a complex sugar biosynthesis pathway (Siu et al 2015). Characterisation of single genes from the cluster mmp1089 - mmp1094 and gene annotation and bioinformatic analyses indicated that MMP1090 is a UDP-glucose 4-epimerase, suggesting that the unique terminal sugar of the archaellin N -glycan might be synthesised from UDP-Glc or UDP-GlcNAc with an essential early step in synthesis catalysed by MMP1090 (Ding et al 2016).…”

Study of the Differentially Expressed Genes in the Pomacea canaliculata Transcriptome after Treatment with Pedunsaponin A

“…The enzyme UDP-glucose 4-epimerase catalyzes the freely reversible interconversion of UDP-glucose to UDP-galactose. As critical precursors for carbohydrate metabolism, UDP-glucose and UDP-galactose play important roles during biosynthetic and metabolic pathways [7,8]. There are two main types of guanylate cyclase (GC): membrane GC (mGC) and soluble GC (sGC).…”