Fig. 3.

Details of structure of the SARS-CoV-2 nsp9 tetramer and function in nucleic acid binding. a, b Details of I_c/d and I_a/b in the helix interface. The molecules in these two interfaces are shown as cartoons and colored and labeled as in Fig. 2a. The expanded boxed area to the right shows a detailed view of the critical residues in the I_c/d and I_a/b interfaces, which are shown as sticks. c Molecules involved in I_b/c. The molecules in this interface are shown as cartoons and colored and labeled as in Fig. 2a. d–f Detailed views of the first, second, and third contact regions in interface I_b/c, respectively. The secondary structures of each contact region are colored and labeled according to Fig. 2a and the critical residues in each region are shown as sticks. g Single-stranded DNA (ssDNA)-binding abilities of SARS-CoV-2 nsp9, as determined by electrophoretic mobility shift assay. h Single-stranded RNA (ssRNA)-binding abilities of SARS-CoV-2 nsp9. The length of ssDNA, the state of SARS-CoV-2 nsp9, and the concentration of proteins used in the reaction system are indicated above the gel