Characterization and representative structures of N-oligosaccharides bound to apolipoprotein H

Area of Science:

• Glycobiology
• Protein Chemistry
• Biochemistry

Background:

• Apolipoprotein H (ApoH) plays roles in lipid transport and immune response.
• Understanding the glycosylation of ApoH is crucial for elucidating its function.
• N-linked carbohydrates significantly impact protein structure and biological activity.

Purpose of the Study:

• To structurally characterize the N-linked carbohydrate chains of apolipoprotein H.
• To investigate the binding properties of ApoH glycans using lectin affinity chromatography.
• To determine the specific glycan structures present on ApoH.

Main Methods:

• Digoxigenin-labeled lectin analysis for carbohydrate chain characterization.
• Concanavalin A (ConA) lectin affinity chromatography to assess glycan binding.
• Elution profiles from ConA chromatography to differentiate glycan affinities.

Main Results:

• ApoH exhibited positive reactivity with SNA, DSA, GNA, PNA, and AAA lectins, but negative with MAA.
• Weak ConA binding indicated complex N-glycans (biantennary or truncated hybrid structures).
• Strong ConA binding suggested N-glycan hybrid structures with high mannose and specific galactose-N-acetylglucosamine sequences.

Conclusions:

• Apolipoprotein H possesses diverse N-glycan structures, including complex and hybrid types.
• The characterized N-glycans, particularly high mannose and hybrid structures, influence ApoH's interaction with Concanavalin A.
• These findings provide insights into the structural heterogeneity of ApoH glycosylation and its functional implications.