Peptide carrier potentiality of Bacillus subtilis levansucrase

A synthetic oligodeoxynucleotide encoding the vasopressin peptide was ligated to the 3' terminal codon of sacB, the structural gene of levansucrase. This gene fusion was integrated into the chromosome of a Bacillus subtilis strain able to overproduce levansucrase. The extracellular production of the hybrid protein, consisting of the whole levansucrase primary sequence plus the nine amino acids of the vasopressin peptide added at the C-terminal end, represented 50-55% of that found for the wild-type levansucrase (20 mg l-1). The purified hybrid protein displayed the same conformational stability, protease insensitivity and enzymic properties as the wild-type levansucrase. However, the rate and the yield of the unfolding-folding transition at the pH and temperature used for bacterial growth were lower in the case of the hybrid protein; the latter also required a higher iron concentration to be completely folded.