The present invention relates to a system for expressing toxic proteins, to an expression vector comprising this system, to a prokaryotic cell transformed with this system, and also to a method for synthesizing a toxic protein using this expression system. The expression system of the invention is characterized in that it comprises successively, in the 5'-3' direction, a nucleotide sequence encoding the Asp-Pro dipeptide and a nucleotide sequence encoding a toxic protein. According to a preferred embodiment of the invention, the expression system also comprises, upstream of the Asp-Pro sequence, a nucleotide sequence encoding a soluble protein. The expression system of the invention makes it possible to construct an expression vector that is useful for transforming a prokaryotic cell such as E. coli, for example in a method for synthesizing the toxic protein.