Mq. Qiao et al., THE CELLULAR LOCATION AND EFFECT ON NISIN IMMUNITY OF THE NISI PROTEIN FROM LACTOCOCCUS-LACTIS N8 EXPRESSED IN ESCHERICHIA-COLI AND L-LACTIS, FEMS microbiology letters, 131(1), 1995, pp. 75-80
Lactococcus lactis cells secreting the lantibiotic nisin, commercially
used for food preservation, must protect their cell membrane against
the pore-forming activity of extracellular nisin. The nisI gene produc
t has been suggested to be a lipoprotein, which due to the location on
the extracellular surface would be an ideal candidate for an immunity
protein. In vivo labelling of NisI from L. lactis N8 expressed in Esc
herichia coli proved that NisI is a lipoprotein. Expression of nisI in
the nisin-sensitive L. lactis MG1614 strain resulted in immunological
ly active protein on the cytoplasmic membrane in comparable amounts to
the immune strain L. lactis N8, but only to slightly increased nisin
immunity, suggesting that additional proteins are needed for full immu
nity.