The Structural Framework and Opening Appearance of the VP1-Pocket of Enteroviruses Correlated with Viral Thermostability.

Enteroviruses (EVs and RVs) are prevalent worldwide and cause various diseases in humans, of which the VP1-pocket is a target of antivirals, with a lipid molecule as a pocket factor to stabilize the virion. However, the characterization of the structure of the VP1-pocket in EVs is poor. Here, we compared the published capsid crystals of EVs and RVs and proposed a structural framework for the VP1-pocket: Frame 1-4, which is located at the CD loop, GH loop, and C-terminus, presenting with an outward opening appearance or not. The non-outward viral strains-CVB3, Echo 11, RV-A81, and RV-B70-are more thermally stable, with a breakpoint temperature (B.T.) of 51~62 °C for genome releasing, which is 4~10 °C higher than its outward temperature of 41~47 °C, and infectivity preservation when treated at 50 °C for 3 min. Its outward versus non-outward opening is correlated significantly with the B.T. for genome release (r = -0.90; p = 0.0004) and infectivity (r = -0.82, p = 0.0039). The energy of Frames 1, 2, and 4, including Van der Waals attractive and repulsive interactions and hydrogen bonds, showed significant correlations with the B.T. (r = -0.67, 0.75, and -0.8; p = 0.034, 0.013, and 0.006, respectively). These characters of the VP1-pocket could be predictors for virion thermostability and aid in the development of vaccines or antivirals.