An efficient expression system for a variant form of the cytotoxic protein alpha-sarcin in Escherichia coli.

An efficient Escherichia coli system for the production of a variant form of the cytotoxic protein alpha-sarcin (delta Ala 1) has been constructed. cDNA encoded alpha-sarcin lacking N-terminal alanine was ligated with the bla signal peptide sequence (the signal sequence of E. coli beta-lactamase localizes the protein in the periplasm) and was inserted into an inducible bacterial expression vector pKTN2-2. When the plasmid introduced into E. coli was expressed in the presence of IPTG, the recombinant product accumulated in the periplasmic space. The product was purified by Affi-Gel Blue followed by Bio-Rex 70 column chromatography. Recombinant alpha-sarcin (delta Ala 1) displayed the properties similar to those of authentic alpha-sarcin isolated from Aspergillus giganteus with respect to its molecular mass and enzymatic activity in ribosomal inactivation. The amount of alpha-sarcin variant produced in the system was estimated to be 1.2 mg/l of culture.