Effect of guanidine hydrochloride and urea on the interaction of 6-thioguanine with human serum albumin: a spectroscopic and molecular dynamics based study

Abstract

6-thioguanine (6-TG) is an antineoplastic, nucleobase guanine, purine analog drug belongs to thiopurine drug-family of antimetabolites. In the present study, we report an experimental approach towards interaction mechanism of 6-TG with human serum albumin (HSA) and examine the chemical stability of HSA in the presence of denaturants such as guanidine hydrochloride (GdnHCl) and urea. Interaction of 6-TG with HSA has been studied by various spectroscopic and spectropolarimeteric methods to investigate what short of binding occurs at physiological conditions. 6-TG binds in the hydrophobic cavity of subdomain IIA of HSA by static quenching mechanism which induces conformation alteration in the protein structure. That helpful for further study of denaturation process where change in secondary structures causes unfolding of protein that also responsible for severance of domain III from rest of the protein part. We have also performed molecular simulation and molecular docking study in the presence of denaturating agents to determine the binding property of 6-TG and the effect of denaturating agents on the structural activity of HSA. We had found that GdnHCl is more effective denaturating agent when compared to urea. Hence, this study provides straight evidence of the binding mechanism of 6-TG with HSA and the formation of intermediate or unfolding transition that causes unfolding of HSA.

Graphical abstract

6-thioguanine bind to HSA through a static quenching procedure by ground-state complex formation and hydrogen bonds and hydrophobic interaction played a major role in the reaction process. GdnHCl and urea denature the HSA by two-state unfolding mechanisms, GdnHCl is more effective denaturant in comparison to urea.

Keywords:

• 6-thioguanine
• circular dichroism
• fluorescence spectroscopy
• guanidine hydrochloride denaturation
• human serum albumin
• urea denaturation
• molecular dynamics

Acknowledgments

MI (ICMR-SRF) is highly thankful to project (BIC/11(12)/2013), Indian Council of Medical Research (ICMR), New Delhi, and also thanks to Basic Scientific Research (UGC-BSR) for providing financial support in this research is gratefully acknowledged. The authors would also like to thank Interdisciplinary Biotechnology Unit, Aligarh Muslim University for providing instrumental facilities.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Basic Scientific Research (UGC-BSR).