Comparative study of the bindings between 3-phenyl-1H-indazole and five proteins by isothermal titration calorimetry, spectroscopy and docking methods

In this study, the interaction between 3-phenyl-1H-indazole (1a) and the fat mass and obesityassociated (FTO) protein was confirmed by isothermal titration calorimetry (ITC). The structure feature of 1a was different from our previously reported FTO inhibitors (radicicol, N-CDPCB and CHTB); the Cl and diol group in structure motif is critical for inhibitors to bind to FTO. In order to test whether there is specificity for the interaction between FTO and 1a, the interactions between 1a and four important proteins (human serum albumin (HSA), pepsin, catalase and trypsin) were investigated by ITC, spectroscopy and molecular docking methods. ITC results showed spontaneous exothermic reactions occurring between 1a and the proteins except trypsin under investigated conditions. The order of the binding affinity of 3-phenyl-1H-indazole is catalase> HSA> FTO> pepsin. Comparison between ITC and spectral results was made. This work will provide the basis for the design of novel inhibitors for FTO.