Figure 1.

Cleavable polyprotein precursor constructs for the heterologous co-expression of two hypothetical pesticidal proteins, Protein 1 and Protein 2, in transgenic plants. The polyprotein precursor includes a cleavable linker peptide (clp) (in green) between the two protein moieties, which is post-translationally processed by exogenous or endogenous proteases (Pro) to release the two mature proteins. (a) Exogenous protease-mediated cleavage. The polyprotein precursor may be cleaved off by a recombinant protease expressed as part of a processing functional unit (cleavage in cis) or after the integration of an independent, co-expressed protease-encoding transgene (cleavage in trans). (b) Endogenous protease-mediated cleavage. Alternatively, the mature proteins may be released by cleavage of a clp recognized by the host plant endogenous proteases. Black arrows on panels (a) and (b) indicate the direction of ribosome-mediated mRNA translation. Red arrows point to protease-susceptible sites on cleavable linker peptides.