Effective unwinding by HCoV-229E nsp13 of partial-duplex DNA and RNA substrates containing extended duplex regions. The structures of the substrates are shown schematically, and radiolabeled strands are marked by asterisks. Reaction products were separated on 2% agarose (A) or 6% polyacrylamide (B) gels. (A) Lanes 1, 6, 11, and 16, heat-denatured substrates; lanes 2, 7, 12 and 17, reactions without protein; lanes 3, 8, 13, and 18, reactions containing HEL and ATP; lanes 4, 9, 14, and 19, reactions containing HEL but no ATP; lanes 5, 10, 15, and 20, reactions containing HEL_KA and ATP. (B) Lane 1, reaction without protein; lane 2, heat-denatured substrate; lane 3, reaction containing HEL and ATP; lane 4, reaction containing HEL_KA and ATP.