FIG 1.

Overview of the heterologous production platform for precursor nisin in B. subtilis. Nisin biosynthesis-associated genes were integrated into the chromosome of B. subtilis via double-crossover reaction. The genes nisAT under the control of the IPTG-inducible promoter P_{hy_spanK} are located in the amyE locus. The genes nisBC controlled by the xylose-inducible promoter P_xylA are located in the thrC locus. RBS1 and RBS2, well-functional RBSs in B. subtilis (see Text S1). NisA, precursor nisin with a leader peptide and a core peptide. NisB, dehydratase which converts serines and threonine residues into dehydroalanine and dehydrobutyrine, respectively. NisC, cyclase which catalyzes the addition of a thiol group in cysteine to an N-terminally located dehydroamino acid, resulting in lanthionine rings. NisT, ABC transporter which transports fully modified NisA. With the induction by extracellular addition of IPTG and xylose, NisA, NisB, NisC, and NisT are expressed in the cells. NisA is modified by NisB and NisC and subsequently is exported by NisT. To activate the antimicrobial ability, the leader peptide could be removed using the in vitro cleavage by the protease NisP. NisB, NisC, and NisT presumably assemble a nisin biosynthetic and transportation machinery within the cytoplasmic membrane.