A lactococcal expression system for engineered nisins.

摘要: Thenisin-producing Lactococcus lactis strain F15876hasbeenmodified anddeveloped foruse as an expression system forengineered nisin variants. Insertional inactivation oftheresident nisAgenehada polar effect on downstream genes,including those involved innisin immunity. However, subsequent chromosomal rearrangements inthis region involving a newlydiscovered insertion element (IS905) generated that was deficient inthenisAgene product butexpressed thosenisin determinants necessaryforprenisin maturation, secretion, andimmunity. Complementation ofthelesion byplasmid-encoded nisA genescontaining site-specific mutations resulted intheexclusive production ofaltered nisins containing specific aminoacidsubstitutions. Nisin isahighly modified peptide antibiotic produced by certain strains ofLactococcus lactis. Itisofgreat interest to thefoodindustry because ofitsefficient antimicrobial activityagainst awiderangeofgram-positive organisms, includingmanyspoilage bacteria andfoodpathogens suchas Listeria, Clostridium, andBacillus species (12, 25). Nisinisamemberofthefamily ofantibiotics termed lantibiotics. Theseunusual polycyclic peptides sharethe structural features ofdehydro residues andintrachain sulfide bridges forming lanthionine andI-methyllanthionine rings.