Fig. 2.

RNA-specific endonuclease activity of SARS-CoV and HCoV-229E nsp15. ss and ds versions of 5′-[³²P] RNA and DNA substrates, respectively, of 1 kb(p) were incubated for 20 min at 37°C without protein (lanes 1, 6, 11, and 16), with HCoV-229E MBP-nsp15_H6360A (HCoV nsp15_mut; lanes 2, 7, 12, and 17), with HCoV-229E MBP-nsp15 (HCoV nsp15; lanes 3, 8, 13, and 18), with SARS-CoV MBP-nsp15_H6678A (SCoV nsp15_mut; lanes 4, 9, 14, and 19) or with SARS-CoV MBP-nsp15 (SCoV nsp15; lanes 5, 10, 15, and 20). Reaction products and RNA size markers were separated in an 8% polyacrylamide gel containing 0.1% SDS.