The Astounding World of Glycans from Giant Viruses

Abstract

Viruses are a heterogeneous ensemble of entities, all sharing the need for a suitable host to replicate. They are extremely diverse, varying in morphology, size, nature, and complexity of their genomic content. Typically, viruses use host-encoded glycosyltransferases and glycosidases to add and remove sugar residues from their glycoproteins. Thus, the structure of the glycans on the viral proteins have, to date, typically been considered to mimick those of the host. However, the more recently discovered large and giant viruses differ from this paradigm. At least some of these viruses code for an (almost) autonomous glycosylation pathway. These viral genes include those that encode the production of activated sugars, glycosyltransferases, and other enzymes able to manipulate sugars at various levels. This review focuses on large and giant viruses that produce carbohydrate-processing enzymes. A brief description of those harboring these features at the genomic level will be discussed, followed by the achievements reached with regard to the elucidation of the glycan structures, the activity of the proteins able to manipulate sugars, and the organic synthesis of some of these virus-encoded glycans. During this progression, we will also comment on many of the challenging questions on this subject that remain to be addressed. CONTENTS AJ 4.2. Chlorovirus N-Glycans AJ 5. Conclusions and Future Perspectives AN Author Information

Functional redundancy revealed by the deletion of the mimivirus GMC-oxidoreductase genes

“…Interestingly, the same GMC-oxidoreductases also compose the surface fibrils of the virions (4,9,17). However, despite their involvement in both the mimivirus genomic fiber structures and the virion surface layer, homologs of these proteins are puzzlingly absent in the laboratory evolved mutant (strain M4) (17), suggesting they may not be essential.…”

Evidence for [2Fe-2S]2+ and Linear [3Fe-4S]1+ Clusters in a Unique Family of Glycine/Cysteine-Rich Fe-S Proteins from Megavirinae Giant Viruses

“…Finally, we aimed to determine whether GciS was conserved within Megavirinae, a proposed subfamily of Mimiviridae. 17 A simple blast search without filtering revealed that the protein was conserved in all members of clade A (mimivirus). Bioinformatic analyses also showed that orthologues of GciS from mimivirus may be found in other members of the subfamily.…”

“…Giant viruses are nucleocytoplasmic large DNA viruses (NCLDVs) with up to 2.8 Mb genomes encoding 1500 proteins, most of them without resemblance to other cellular or viral proteins (ORFans). , Giant viruses are found in diverse habitats and infect eukaryotes, mostly protists and microalgae (reviewed in ref ). The first giant virus, mimivirus, was discovered in 2003.…”

“…Finally, we aimed to determine whether GciS was conserved within Megavirinae , a proposed subfamily of Mimiviridae . A simple blast search without filtering revealed that the protein was conserved in all members of clade A (mimivirus).…”

Deciphering Regulatory Proteins of Prenylated Protein via the FRET Technique Using Nitroso-Based Ene-Ligation and Sequential Azidation and Click Reaction

“…Proteins are biopolymers that exist broadly in living organisms, playing a wide range of pivotal roles in cell growth, differentiation, movement, catalyzing reactions, and more . Despite the 20 natural l -form amino acids, cells use more than 400 modifications, namely, post-translational modifications (PTMs), to accommodate environmental change, including phosphorating, acetylation, , glycosylation, , ubiquitylation, lipidation, , and beyond. In addition, chemical modifications targeting amino acid residues with high selectivity have also been developed in the past several decades, complementing natural modifications catalyzed by varied enzymes. , The lysine, cysteine, tyrosine, , arginine, histidine, methionine, , and tryptophan have been comprehensively investigated, and a wide range of reagents with highly selective manners have been explored (Figure A) .…”