Secretion-dependent proteolysis of recombinant proteins is associated with inhibition of cell growth in Escherichia coli

The antigenic C-terminus of VP60 capsid protein from rabbit haemorrhagic disease virus was produced in E. coli under the control of an IPTG-inducible T7 promoter. Two different but closely related constructs were designed, carrying either a periplasmic secretional signal or a T7 detection tag at the N-terminus of the viral segment. The cytoplasmic protein is produced in high yields whereas the periplasmic version is hardly detected in Western blot, due to its immediate degradation after synthesis. Recombinant cultures producing the periplasmic, but not the cytoplasmic form show a dramatic arrest of cell growth after induction of gene expression, indicative of toxicity associated to the recombinant protein itself or to its proteolytic processing. Molecular mechanisms for such toxic effects are discussed.