Genes Involved in the Endoplasmic Reticulum N-Glycosylation Pathway of the Red Microalga Porphyridium sp.: A Bioinformatic Study

Abstract

N-glycosylation is one of the most important post-translational modifications that influence protein polymorphism, including protein structures and their functions. Although this important biological process has been extensively studied in mammals, only limited knowledge exists regarding glycosylation in algae. The current research is focused on the red microalga Porphyridium sp., which is a potentially valuable source for various applications, such as skin therapy, food, and pharmaceuticals. The enzymes involved in the biosynthesis and processing of N-glycans remain undefined in this species, and the mechanism(s) of their genetic regulation is completely unknown. In this study, we describe our pioneering attempt to understand the endoplasmic reticulum N-Glycosylation pathway in Porphyridium sp., using a bioinformatic approach. Homology searches, based on sequence similarities with genes encoding proteins involved in the ER N-glycosylation pathway (including their conserved parts) were conducted using the TBLASTN function on the algae DNA scaffold contigs database. This approach led to the identification of 24 encoded-genes implicated with the ER N-glycosylation pathway in Porphyridium sp. Homologs were found for almost all known N-glycosylation protein sequences in the ER pathway of Porphyridium sp.; thus, suggesting that the ER-pathway is conserved; as it is in other organisms (animals, plants, yeasts, etc.).

Insight into glucosidase II from the red marine microalgaPorphyridiumsp. (Rhodophyta)

“…Bioinformatic studies using our in‐house c‐DNA genome (Levy‐Ontman et al. ) indicated that the algal GANAB glycoenzyme is a dimer of α (125 kDa) and β subunit (58 kDa), sharing homology to other ortholog enzymes derived from a range lower to more complex eukaryotes. Indeed, the high similarity of the algal glycoenzyme to its orthologs suggests that these exo‐type glycosidases that act with a retention mechanism (releasing α‐D‐glucopyranose with retention of the configuration in the anomeric position; Chiba ) are conserved across evolution eras and its importance is highlighted in eukaryotes in general and photosynthetic organisms in particular.…”

“…) and by identifying the encoded genes related to the ER N‐glycosylation pathway (Levy‐Ontman et al. ). It appears that the ER N‐glycosylation pathway in Porphyridium sp.…”

“…We suggested that the Golgi may involve novel glycosyltransferases that are responsible for the addition of unusual groups such as the xylose and methylated residues that are not typical to eukaryotic N‐glycosylation pathways studied to date (Levy‐Ontman et al. , ).…”

“…Recently, we reported on the N-glycan structures and N-glycosylation pathways in the red microalga Porphyridium sp. based on biochemical analysis of the N-glycan of the cell wall glycoprotein (Levy-Ontman et al 2011) and by identifying the encoded genes related to the ER Nglycosylation pathway (Levy-Ontman et al 2014). It appears that the ER N-glycosylation pathway in Porphyridium sp.…”

Contribution to study the glycoprotein ligands of the cerebellar soluble lectin in human K562 tumour cells

“…Asn-X-(Ser/thr), however, the precise regulation process implicated in the N-glycosylation is still unknown [45,46]. It has been suggested that the N-glycosylation concerns only the accessible asparagine.…”