Arginyl-binding sites of human plasminogen

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Chemistry

Background:

• Plasminogen is a key protein in the fibrinolytic system.
• Understanding ligand-binding sites is crucial for drug development and molecular diagnostics.

Purpose of the Study:

• To investigate the localization and specific features of lysine- and arginyl-binding sites in Lys-plasminogen and its fragments.
• To characterize the interactions of these binding sites with different ligands.

Main Methods:

• Affinity chromatography using sorbents with arginine-like ligands (homoarginine-agarose and lysine-agarose).
• Investigation of Lys-plasminogen, its heavy chain, and specific fragments (K1-3, K4, K5).

Main Results:

• Lysine-binding sites in Lys-plasminogen, heavy chain, and K1-3 fragment interact with the guanidyl-carboxyl pair on homoarginine-agarose.
• A distinct lysine-binding site in domain K4 interacts with an amine-carboxyl pair on lysine-agarose but not guanidyl-carboxyl.
• Plasminogen possesses three arginyl-binding sites interacting with the guanidyl group of homoarginine-agarose.
• Two arginyl-binding sites correspond to known benzamidine-binding sites in domain K5 and the plasmin light chain.
• A novel, previously uncharacterized arginyl-binding site was identified in fragment K1-3, which does not interact with benzamidine-agarose.

Conclusions:

• Specific lysine-binding sites exhibit differential interactions based on ligand chemical properties.
• Plasminogen contains multiple arginyl-binding sites, including a newly identified site in the K1-3 fragment.
• These findings provide detailed insights into the molecular interactions of plasminogen, relevant for understanding its function and for therapeutic targeting.