The possible signal sequence capable of transporting the Cl-amylase from B. circulans has been analyzed with in vitro mutagenesis techniques. A residue in the NH₂-terminal region near to the postulated cleavase site was changed by site-directed muta...
The possible signal sequence capable of transporting the Cl-amylase from B. circulans has been analyzed with in vitro mutagenesis techniques. A residue in the NH₂-terminal region near to the postulated cleavase site was changed by site-directed mutagenesis from a serine into proline and threonine. Comparison of Cl-amylase acitivity outside and inside the cell in strains containing the cloned wild type and mutagenised genes showed that this single amino acid prevents largely the translocation of the enzyme in the periplasmic space: in transformed E. coli the proline -mutant Cl-amylase showed 5% secretion of wild type Cl-amylase and threonine-mutant Cl-amylase.