Selection of functional 2A sequences within foot-and-mouth disease virus; requirements for the NPGP motif with a distinct codon bias

Structure of the FMDV O1 Kaufbeuren (O1K) cDNA and its derivatives. (A) The plasmid-encoded amino acids and the corresponding nucleotide sequences at the 2A/2B junction are shown. The FMDV O1K degenerate codon mutants were produced as described in the text using the mutant pT7S3 plasmids encoding the N¹⁶A, P¹⁷A, G¹⁸A, and P¹⁹A substitutions as templates. The full-length plasmid pools were linearized using HpaI prior to in vitro transcription and virus rescue. The locations of the HpaI and ApaI restriction sites that were used are marked. (N) A mixture of the 4 nucleotides. (B) Chromatograms and sequences of the FMDV cDNA corresponding to the NPGP motif at the 2A/2B junction. Degenerate positions showing the presence of multiple nucleotides are marked with an N (in bold type). The color code in the chromatograms is as follows: A (red), T (green), G (yellow), C (blue).