LAUSR

Southern rice black-streaked dwarf virus (SRBSDV) P9-1 octameric protein accumulates viroplasms in SRBSDV-infected plant and insect cells, our previous studies found α-amino phosphonate drug—dufulin had a micromole affinity with SRBSDV P9-1. Now we focus our studies on the SRBSDV P9-1 crystal structure and use it as the target for α-amino phosphonate derivatives. The structure of the SRBSDV P9-1 cylindrical octamer was determined to a 2.2 Å resolution using X-ray crystallography, this structure was composed of nine α-helices, nine β-sheets and a series of interconnecting loops. The structures of all eight subunits were nearly identical, except for some differences in the β-sheet core. There were six different sites (R20K, V109D, F164T, V123L, C124L and V128T) present between the SRBSDV P9-1 and the previously reported RBSDV P9-1 crystal structure. Fluorescence titration, isothermal calorimetry and microscale thermophoresis experiments showed that α-amino phosphonate derivatives GUFCC-013 and GUFCC-023 bound to SRBSDV P9-1 with micromole binding affinities. These results will provide important help for the further improvement of the lead compound and develop the potential anti-SRBSDV