Interaction of Esculetin with Alpha-2-Macroglobulin: Biochemical and Biophysical Approaches

Abstract

Esculetin is found in various natural plant products and has beneficial biological and biochemical activities. Alpha2-macroglobulin (α₂M) is a high molecular weight homotetrameric glycoprotein with many diversified and complex functions. Primarily known for its ability to inhibit a broad spectrum of proteinases, α₂M is involved in the binding, transportation, and regulation of many proteins, cytokines, hormones, etc. α₂M has been reported to bind a variety of molecules, including drugs, and may play an important role in their distribution and elimination. In this report we describe our research on the mechanism of interaction between esculetin and α₂M by various techniques including fluorescence, UV-visible spectroscopy, circular dichroism (CD) and isothermal titration calorimetry (ITC), under physiological conditions. Esculetin was found to form a complex with α₂M, which involves primarily hydrogen bonding with a small contribution from van der Waals forces. Moreover, the binding of esculetin to α₂M did not induce significant changes in the secondary structure of the complex as determined by CD analysis.

Keywords:

• Alpha-2-macroglobulin
• coumarin
• esculetin
• polyphenol
• protein-ligand complex
• proteinase inhibitor

Acknowledgments

AAR and FHK wish to thank the Department of Science and Technology (DST-Fund for the Improvement of Science and Technology Infrastructure in Higher Educational Institutions), India and University Grants Commission (UGC-Special Assistance Program), India, for the departmental financial support and UGC-BSR (Basic Scientific Research), India for providing a fellowship to AAR.

Disclosure statement

No potential conflict of interest was reported by the authors.