Fig. 5
The RNA binding activity of MERS-CoV N fragments. a Purification of various N fragments. Purification of the full-length (FL) N protein and its subdomains N(1–263), N(264–413), N(1–156), and N(239–413) followed the procedures as described in the legend of Fig. 4. Coomassie blue staining and Western blot analysis are shown. b Schematic representation of the N subdomains and the filter binding assay. The N protein of coronavirus is organized into two structural domains (NTD and CTD) separated by a flexible linker. The NTD structure mainly has an antiparallel β-sheet core domain, whereas the CTD is composed of mainly α-helices [29, 30, 33]. The secondary structural elements are indicated by triangles for β-sheets and cylinders for α-helices, and those shown above the N protein fragments (closed boxes) correspond to the structure of the MERS-CoV N protein, whereas those shown under the boxes correspond to the SARS-CoV N protein. The filter binding assay was conducted with the biotin-SL19805ME and increasing amounts of the N proteins and BSA control as indicated