BIOSYNTHESIS OF LANTIBIOTIC NISIN - POSTTRANSLATIONAL MODIFICATION OFITS PREPEPTIDE OCCURS AT A MULTIMERIC MEMBRANE-ASSOCIATED LANTHIONINESYNTHETASE COMPLEX

The lantibiotic nisin of Lactococcus lactis is matured from a ribosoma lly synthesized prepeptide by posttranslational modification. Genetic and biochemical evidence suggests that genes nisB and nisC of the nisi n gene cluster encode proteins necessary for prenisin modification. In activation of both genes resulted in complete loss of nisin production . The preparation of membrane vesicles revealed that NisB and NisC are attached to the cellular membrane, and co-immunoprecipitation experim ents showed that they are associated with each other. By using the yea st two-hybrid system, which is a highly sensitive method to unravel pr otein-protein interactions, we could show that the nisin prepeptide ph ysically interacts with the NisC protein, suggesting that NisC contain s a binding site for prenisin. This was also confirmed by co-immunopre cipitation of the NisC protein and the NisA prepeptide by antibodies d irected against the leader sequence of the nisin prepeptide. The two-h ybrid analysis also confirmed the interaction between NisB and NisC as well as the interaction between NisC and the NisT ABC transporter. A minor interaction was also indicated between prenisin and the NisB pro tein. Furthermore, the two-hybrid investigations also revealed that at least two molecules of NisC and two molecules of NisT are part of the modification and transport complex. Our results suggest that lantibio tic maturation and secretion occur at a membrane associated multimeric lanthionine synthetase complex consisting of proteins NisB, NisC, and the ABC transporter molecules NisT.