Mutagenesis Studies and Structure-function Relationships for GalNAc/Gal-Specific Lectin from the Sea Mussel...

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• The GalNAc/Gal-specific lectin from Crenomytilus grayanus (CGL) possesses anticancer properties and a unique β-trefoil fold.
• Previous studies identified three carbohydrate-binding sites in CGL and its interaction with globotriose (Gb3) and mucin-type glycoproteins often found on cancer cells.

Purpose of the Study:

• To investigate the in silico binding mechanisms of CGL with its ligands: galactose, globotriose, and mucin.
• To evaluate the role of specific amino acid residues within the carbohydrate-binding sites in CGL's activity through site-directed mutagenesis.

Main Methods:

• In silico analysis of CGL-ligand binding mechanisms.
• Site-directed mutagenesis to substitute key amino acid residues (His37, His129, Glu75, Asp127, His85, Asn27, Asn119) with alanine.
• Assessment of the impact of mutations on CGL's mucin-binding activity.

Main Results:

• Alanine substitutions of His37, His129, Glu75, Asp127, His85, Asn27, and Asn119 significantly affected CGL's mucin-binding activity.
• The affinity of CGL to its ligands is dependent on ligand structure, correlated with the number of hydrogen bonds in the CGL-ligand complexes.
• Identified critical amino acid residues essential for CGL's lectin activity.

Conclusions:

• Specific amino acid residues are crucial for the mucin-binding activity of CGL.
• Understanding the molecular interactions governing CGL-ligand binding can inform the design of synthetic analogs with improved carbohydrate-binding properties.
• CGL shows promise as a biosensor for cancer diagnostics due to its specific recognition of cancer-associated glycans.