Binding studies between cytosinpeptidemycin and the superfamily 1 helicase protein of tobacco mosaic virus

Tobacco mosaic virus (TMV) helicases play important roles in viral multiplication and interactions with host organisms. They can also be targeted by antiviral agents. Cytosinpeptidemycin has a good control effect against TMV. However, the mechanism of action is unclear. In this study, we expressed and purified TMV superfamily 1 helicase (TMV-Hel) and analyzed its three-dimensional structure. Furthermore, the binding interactions of TMV-Hel and cytosinpeptidemycin were studied. Microscale thermophoresis and isothermal titration calorimetry experiments showed that cytosinpeptidemycin bound to TMV-Hel with a dissociation constant of 0.24–0.44 μM. Docking studies provided further insights into the interaction of cytosinpeptidemycin with the His375 of TMV-Hel. Mutational and Microscale thermophoresis analyses showed that cytosinpeptidemycin bound to a TMV-Hel mutant (H375A) with a dissociation constant of 14.5 μM. Thus, His375 may be the important binding site for cytosinpeptidemycin. The data are important for designing and synthesizing new effective antiphytoviral agents.