Dengue virus protease activity modulated by dynamics of protease cofactor

The viral protease domain (NS3pro) of dengue virus is essential for virus replication and its cofactor NS2B is indispensable for the proteolytic function. Although several NS3pro-NS2B complex structures have been obtained, the dynamic property of the complex remains poorly understood. Using NMR relaxation techniques, here we found that NS3pro-NS2B exists in both closed and open conformations which are in dynamic equilibrium on a sub-millisecond timescale in aqueous solution. Our structural information indicates that the C-terminal region of NS2B is disordered in the open conformation but folded in the closed conformation. Using mutagenesis, we showed that the closed-open conformational equilibrium can be shifted by changing NS2B stability. Moreover, we revealed that the proteolytic activity of NS3pro-NS2B correlates well with the population of the closed conformation. Our results suggest that the closed-open conformational equilibrium can be used by both nature and man to control the replication of dengue virus. Statement of SignificanceThe dengue virus protease is an attractive target for drug development against dengue fever as it is essential for virus replication. However, its structure-based drug development has been unsuccessful due to the shallow substrate-binding pocket. The study presented here demonstrates for the first time that the protease activity can be reduced dramatically by shifting the closed-open conformational equilibrium of the protease in complex with its cofactor from the majority of a closed conformation to the majority of an open conformation. Moreover, our work clarifies the structure of the open conformation which has been elusive for a long time. Our results also suggest an alternative method for designing protease inhibitors based on the closed-open conformational equilibrium.