Glycosylated proteins in the protozoan alga Euglena gracilis: a proteomic approach

Abstract Protein glycosylation, and in particular N-linked glycans, is a hallmark of eukaryotic cells and has been well-studied in mammalian cells and parasites. However, little research has been conducted to investigate the conservation and variation of protein glycosylation pathways in other eukaryotic organisms. Euglena gracilis is an industrially important microalga, used in the production of biofuels and nutritional supplements. It is evolutionarily highly divergent from green algae and more related to kinetoplastid pathogens. It was recently shown that E. gracilis possesses the machinery for producing a range of protein glycosylations and make simple N-glycans, but the modified proteins were not identified. This study identifies the glycosylated proteins, including transporters, extracellular proteases, and those involved in cell surface signalling. Notably, many of the most highly expressed and glycosylated proteins are not related to any known sequences and are, therefore, likely to be involved in important novel functions in Euglena. Lectin affinity and proteomics identified glycosylated and extracellular proteins, including transporters, proteases and signalling components, in the evolutionarily and industrially important protozoan alga Euglena gracilis.