Coxsackie virus B3 genes (Nancy strain, GenBank: M33854.1) were individually PCR-amplified from a genomic plasmid using primers containing restrictions site overhangs, digested, and ligated into the pcDNA4/TO plasmid (Invitrogen) that has been engineered to fuse a 2xStrep tag to the C-terminus of proteins cloned into the multiple cloning site47 (link). Mutations for 2A C107A and 3C C147A were introduced by site-directed mutagenesis.