The L-Rhamnose Biosynthetic Pathway in : Identification and Characterization of UDP-D-Glucose 4,6-dehydratase.

is the causative agent of one of the most widespread sexually transmitted diseases in the world. The adhesion of the parasite to the vaginal epithelial cells is mediated by specific proteins and by a complex glycan structure, the lipoglycan (TvLG), which covers the pathogen surface. L-rhamnose is an important component of TvLG, comprising up to 40% of the monosaccharides.

Expanding the Occurrence of Polysaccharides to the Viral World: The Case of Mimivirus.

The general perception of viruses is that they are small in terms of size and genome, and that they hijack the host machinery to glycosylate their capsid. Giant viruses subvert all these concepts: their particles are not small, and their genome is more complex than that of some bacteria. Regarding glycosylation, this concept has been already challenged by the finding that Chloroviruses have an autonomous glycosylation machinery that produces oligosaccharides similar in size to those of small viruses (6-12 units), albeit different in structure compared to the viral counterparts.

The -glycan structures of the antigenic variants of chlorovirus PBCV-1 major capsid protein help to identify the virus-encoded glycosyltransferases.

The chlorovirus chlorella virus 1 (PBCV-1) is a large dsDNA virus that infects the microalga NC64A. Unlike most other viruses, PBCV-1 encodes most, if not all, of the machinery required to glycosylate its major capsid protein (MCP). The structures of the four -linked glycans from the PBCV-1 MCP consist of nonasaccharides, and similar glycans are not found elsewhere in the three domains of life.

The rare sugar -acetylated viosamine is a major component of Mimivirus fibers.

The giant virus Mimivirus encodes an autonomous glycosylation system that is thought to be responsible for the formation of complex and unusual glycans composing the fibers surrounding its icosahedral capsid, including the dideoxyhexose viosamine. Previous studies have identified a gene cluster in the virus genome, encoding enzymes involved in nucleotide-sugar production and glycan formation, but the functional characterization of these enzymes and the full identification of the glycans found in viral fibers remain incomplete. Because viosamine is typically found in acylated forms, we suspected that one of the genes might encode an acyltransferase, providing directions to our functional annotations.

The Autonomous Glycosylation of Large DNA Viruses.

Glycosylation of surface molecules is a key feature of several eukaryotic viruses, which use the host endoplasmic reticulum/Golgi apparatus to add carbohydrates to their nascent glycoproteins. In recent years, a newly discovered group of eukaryotic viruses, belonging to the Nucleo-Cytoplasmic Large DNA Virus (NCLDV) group, was shown to have several features that are typical of cellular organisms, including the presence of components of the glycosylation machinery. Starting from initial observations with the chlorovirus PBCV-1, enzymes for glycan biosynthesis have been later identified in other viruses; in particular in members of the Mimiviridae family.

Giant virus Megavirus chilensis encodes the biosynthetic pathway for uncommon acetamido sugars.

Giant viruses mimicking microbes, by the sizes of their particles and the heavily glycosylated fibrils surrounding their capsids, infect Acanthamoeba sp., which are ubiquitous unicellular eukaryotes. The glycans on fibrils are produced by virally encoded enzymes, organized in gene clusters.

Effects of microRNAs on fucosyltransferase 8 (FUT8) expression in hepatocarcinoma cells.

Fucosyltransferase 8 (FUT8) catalyzes the transfer of α1,6-linked fucose to the first N-acetylglucosamine in N-linked glycans (core fucosylation). Increased core fucosylation has been reported during hepatocarcinogenesis, in both cell-associated and secreted proteins. Accordingly, increased core fucosylation of α-fetoprotein and α1-antitrypsin is currently used as a diagnostic and prognostic indicator.

Characterization of a UDP-N-acetylglucosamine biosynthetic pathway encoded by the giant DNA virus Mimivirus.

Mimivirus is a giant DNA virus belonging to the Megaviridae family and infecting unicellular Eukaryotes of the genus Acanthamoeba. The viral particles are characterized by heavily glycosylated surface fibers. Several experiments suggest that Mimivirus and other related viruses encode an autonomous glycosylation system, forming viral glycoproteins independently of their host.

Structure of N-linked oligosaccharides attached to chlorovirus PBCV-1 major capsid protein reveals unusual class of complex N-glycans.

The major capsid protein Vp54 from the prototype chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1) contains four Asn-linked glycans. The structure of the four N-linked oligosaccharides and the type of substitution at each glycosylation site was determined by chemical, spectroscopic, and spectrometric analyses. Vp54 glycosylation is unusual in many ways, including: (i) unlike most viruses, PBCV-1 encodes most, if not all, of the machinery to glycosylate its major capsid protein; (ii) the glycans are attached to the protein by a β-glucose linkage; (iii) the Asn-linked glycans are not located in a typical N-X-(T/S) consensus site; and (iv) the process probably occurs in the cytoplasm.