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The asparagine-linked sugar chains of subcomponent C1q of the first component of human complement
Insights
Human C1q, a complement system component, has six N-linked sugar chains in its globular region. Researchers elucidated the complex structures of these carbohydrate chains using advanced analytical techniques.
Area of Science:
- Glycobiology
- Immunochemistry
- Proteomics
Background:
- Human C1q is the first component of the classical complement pathway.
- C1q contains six asparagine-linked carbohydrate chains.
- These sugar chains are localized to the COOH-terminal globular region.
Purpose of the Study:
- To determine the precise structures of the asparagine-linked sugar chains in human C1q.
- To characterize the glycosylation pattern of the C1q globular region.
Main Methods:
- Carbohydrate chains were released from the C1q polypeptide by hydrazinolysis.
- Structural analysis was performed using sequential exoglycosidase digestion.
- Methylation analysis was employed to confirm linkage positions.
Main Results:
- The study confirmed the presence of six N-linked sugar chains per molecule of human C1q.
- Detailed structural elucidation revealed complex N-glycan structures.
- Specific linkages and branching patterns, including sialylation and fucosylation, were identified.
Conclusions:
- The N-linked glycans in human C1q are complex and located in the globular head region.
- The elucidated structures provide insights into the functional role of glycosylation in C1q.
- This detailed glycan characterization contributes to understanding complement system regulation.
Abstract:
Human C1q, a subcomponent of the first component of complement, contains six asparagine-linked sugar chains in 1 molecule. The sugar chains are exclusively located in the COOH-terminal globular region which is composed of 330 amino acid residues. The sugar chains were liberated from the polypeptide portion by hydrazinolysis, and their structures were studied by the combination of sequential exoglycosidase digestion and methylation analysis. Based on the results, the structures NeuAcalpha2 leads to 6Galbeta1 leads to 4GlcNAcbeta1 leads to 2Manalpha1 leads to 6(+/- NeuAcalpha2 leads to 6Galbeta1 leads to 4GlcNAcbeta1 leads to 2Manalpha1 leads to 3)Manbeta1 leads to 4GlcNAcbeta1 leads to 4(+/-Fucalpha1 leads to 6)GlcNAc were confirmed.