The diversity of glycan chains in jellyfish mucin of three Cubozoan species: the contrast in molecular evolution rates of the peptide chain and Glycans.

This article focuses on the analysis of the O-glycan composition of qniumucin (Q-mucin), a mucin-type glycoprotein extracted from three Cubozoan jellyfish species, following optimization of purification protocols. The study found that while the amino acid sequence of the tandem repeat (TR) region in Q-mucin is highly conserved across these Cubozoan species and also shared with Scyphozoan jellyfish—indicating evolutionary stability over more than 500 million years—the glycan chains exhibit significant diversity, particularly in the amounts of acidic moieties and disaccharide content. This contrast is attributed to the differing mechanisms and evolutionary time scales of protein biosynthesis (for the TR region) versus post-translational modifications (for glycan chains). The authors propose a hierarchical "double-decker" model in which the conserved peptide and initial O-glycosylation form a stable base, while the glycan modifications evolve rapidly to support species-specific ecological adaptations, balancing species conservation with diversity acquisition.