A schematic diagram of the biosynthesis of nisin A. Nisin A is ribosomally synthesized as an inactive prepeptide, NisA, consisting of an N-terminal leader sequence attached to a propeptide moiety. Modification enzymes, NisB and NisC, dehydrate and cyclize the propeptide respectively, and subsequently the ABC transporter, NisT, translocates the modified prepeptide into the extracellular space. The protease, NisP, then cleaves off the leader peptide, releasing the mature (active form) nisin A. The lipoprotein NisI that can bind to nisin A, and the multi-protein ABC transporter complex NisFEG, which expels nisin A from the cell, comprise the self-immunity system for nisin A. Two-component regulation system that is responsible for the up-regulation of the nisin gene cluster is composed of a histidine kinase, NisK, and a response regulator, NisR. Nisin A serves as the signal peptide that activates this regulation system.