Pharmaceutica Analytica Acta

Abstract

Dynamics of HSP60-Cypd Binding Studied with Surface Plasmon Resonance

Ekaterina A Korobkova

Objectives: The binding of chaperonin HSP60 to cyclophilin D (CypD) represents an oncogenic pathway that prevents mitochondria from undergoing permeability transition pore (PTP) opening. Thus HSP60 may be considered as an attractive target for the design of chemical inhibitors. The complexity of the HSP60 structure prevents the use of standard screening methods. The present study was aimed to analyze the dynamics of CypD interactions with different HSP60 domains. Method: Surface plasmon resonance (SPR) technology was employed. Antibodies that map to various regions of the HSP60 were immobilized on a CM5 biosensor chip using amino-coupling chemistry. HSP60 was attached to various antibodies on the chip resulting in different orientations of the protein, and the kinetics of its binding to HSP60 was analyzed. Results: The dissociation rate constants for HSP60-CypD interactions ranged between 5.5 × 10-4 s-1 and 16 × 10-4 s-1. The dissociation equilibrium constants varied from 15.8 nM to 43.5 nM. An antibody recognizing a region between residues 50 and 100 in the equatorial domain of HSP60 prevented its association with CypD. Conclusion: SPR technology proved successful in the analysis of the interactions between CypD and HSP60 subunits. The binding strength was comparable to that of a relatively strong antibody-antigen binding. The preferential binding of CypD to a specific domain within HSP60 subunit suggests the possibility of designing a molecular antagonist.