Voltage-Dependent Anion Channel-1, a Possible Ligand of Plasminogen Kringle 5

Molecular recognition and binding between human plasminogen Kringle 5 and α-chain of human complement component C3b by frontal chromatography and dynamics simulation

The binding and molecular recognition between α-chain of human complement C3b (α-chain of C3b) and human plasminogen Kringle 5 (Kringle 5) were studied and explored by frontal chromatography and dynamics simulation in the combination of bio-specific technologies. The specific interaction between the α-chain of C3b and Kringle 5 was initially confirmed by ligand blot and ELISA (Kd = 4.243×10-6 L/mol). Furthermore, the binding determination conducted via frontal chromatography showed that the presence of a single binding site between them, with the binding constant of 2.98 × 105 L/mol. Then the molecular recognition by dynamics simulation and molecular docking showed that there were 9 and 13 amino acid residues respective in the Kringle 5 and α-chain of C3b directly implicated in the binding and the main stabilizing forces were electrostatic force (-55.99 ± 11.82 kcal/mol) and Van der Waals forces (-42.70 ± 3.45 kcal/mol). Additionally, a loop structure (65-71) in Kringle 5 underwent a conformational change from a random structure to an α-helix and a loop structure (417-425) in α-chain of C3b was closer to the molecular center, both of them were more conducive to the binding between them. Meanwhile, the involvement of the lysine binding site of Kringle 5 played an important role in the binding process. In addition, the erythrocyte-antibody complement rosette assay substantiated that the presence of Kringle 5 hindered the transportation of α-chain of C3b to antigen-antibody complex in a dose-dependent manner. These findings collectively indicated that the α-chain of C3b is very likely a receptor protein for Kringle 5, which provides a methodology for other similar investigations and valuable insights into expansion of the pharmacological effects and potential application of Kringle 5 in immune-related diseases.

Molecular recognition and interaction between human plasminogen Kringle 5 and voltage-dependent anion channel-1 by biological specificity technologies and molecular dynamic simulation

Voltage-dependent anion channel-l (VDAC-1) can bind with plasminogen Kringle 5 as the cell surface receptor and induce cell apoptosis, but the detailed information of binding is not clear yet. Thus, the mutual recognition and binding were investigated here utilizing frontal affinity chromatography, surface plasma resonance, mutation analysis combining molecular dynamics simulation. The results showed that Kringle 5 binds with VDAC-1 in equimolar driven mainly by electrostatic force, with 15 amino acid residues participating in Kringle 5 and 21 in VDAC-1. The observed conformational changes indicated the automatic structure regulation providing these two proteins suitable conformations and spatial surroundings for the tighter and stabler binding. Moreover, Glu29 in Kringle 5 was speculated as the key residue maintaining the largest energy contribution. Therefore, this work provided precise information for the recognition and binding of Kringle 5 with VDAC-1 that is valuable for the corresponding treatment of tumours or other angiogenic diseases.