Fig 2. Mutations at the 3B-3C boundary disrupt P3 polyprotein processing.

Plasmid constructs expressing wild-type FMDV P3 or the 3B3/2 chimeric mutant polyprotein were used to assemble coupled transcription/translation reactions with [³⁵S] labelled methionine. Reactions were incubated for 40 minutes before addition of excess unlabelled methionine/cysteine, samples were taken at regular intervals and reaction stopped by the addition of 2 x Laemmli buffer. (A) Proteins were separated on 12% SDS-PAGE and visualised by autoradiography. The positions of FMDV protein products are indicated by arrows, the 3D* product represents a degradation or cleavage product of 3D^pol (as confirmed by Western blot, see S2 Fig). Control reactions were assembled using empty expression vector alone. The proportion of uncleaved P3 (B) and 3D^pol (C) product was quantified as a percentage of the total 3D^pol containing products (n = 2 ± SD).