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How a plant lectin recognizes high mannose oligosaccharides.
Abel Garcia-Pino1, Lieven Buts, Lode Wyns
1Laboratorium voor Ultrastructuur, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel, Belgium.
Plant Physiology
|June 9, 2007
Summary
Pterocarpus angolensis seed lectin binds high mannose oligosaccharides in a unique way. Glycoprotein context significantly enhances lectin binding affinity for mannose-9, revealing its biological relevance.
Area of Science:
- Carbohydrate Chemistry
- Structural Biology
- Biochemistry
Background:
- Lectins are proteins that bind carbohydrates, playing roles in biological recognition.
- Pterocarpus angolensis seed lectin (PASL) is a plant lectin with potential applications.
- High mannose oligosaccharides are crucial in protein glycosylation and cellular processes.
Purpose of the Study:
- To elucidate the binding mode of PASL with high mannose oligosaccharides.
- To determine the binding affinity of PASL for various mannose oligosaccharides.
- To investigate the influence of glycoprotein context on PASL-ligand interactions.
Main Methods:
- X-ray crystallography was used to determine the complex structure of PASL with mannose oligosaccharides (Man-5 to Man-9).
- Isothermal titration calorimetry (ITC) was employed to quantify binding affinities.
- Glycoprotein (soybean agglutinin) was used to assess binding in a complex biological context.
Main Results:
- PASL binds all studied oligomannosides (Man-5 to Man-9) in a single, conserved orientation, utilizing a specific tetrasaccharide sequence.
- Isothermal titration calorimetry confirmed the monovalent binding of Man-9.
- A four-fold increase in binding affinity was observed when Man-9 was presented within a glycoprotein context.
Conclusions:
- PASL exhibits a specific and conserved binding mode for high mannose oligosaccharides.
- The presentation of mannose oligosaccharides within a glycoprotein significantly enhances binding affinity to PASL.
- These findings provide insights into the molecular basis of lectin-carbohydrate interactions and their biological implications.
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