Nucleotide sequence and characterization of the cell envelope proteinase plasmid in Lactococcus lactis subsp cremoris HP

Aims: The major cell envelope proteinase (lactocepin; EC 3.4.21.96) produce d by Lactococcus lactis cheese starter bacteria is required for starter gro wth and acid production in milk. The aim of this study was to characterize a lactocepin plasmid from a L. lactis subsp. cremoris cheese starter strain . Methods and Results: A restriction map of the lactocepin plasmid pHP003 fro m strain HP was constructed, fragments were cloned in Escherichia coli vect ors, and the complete DNA sequence (13 433 bp) was determined. Among 120 in dustrial L. lactis starter strains screened, five contained the same specif icity-type lactocepin as pHP003. The lactocepin gene in these strains was i nvariably linked with a partially-deleted abiB gene. Conclusions: The lactocepin specificity type of strain HP, conferred by a k nown configuration of key residues, is relatively uncommon. The gene is inv ariably linked with a partially deleted abiB gene on each lactocepin plasmi d. Significance and Impact of the Study: This is the first complete sequence r eported for a lactocepin plasmid, and provides the basis for better underst anding, or manipulation, of lactocepin production.