Lactococcus lactis subsp. lactis IPLA 972 produces a polypeptide bacteriocin of 7.5 kDa which has a bactericidal effect on sensitive lactococci. inhibiting septum formation in dividing cells. The active form is a monomer that is metastable under normal conditions but is stabilised by glycerol. The NMR structure of Lcn972 shows a beta-sandwich comprising two three-stranded antiparallel beta-sheets. Detaching the final strand could allow the sandwich to open, and the irreversible unfolding leads to a loss of antibacterial activity. Covalent linkage of the final strand should increase the stability of Lcn972 and facilitate the study of its interaction with lipid II. (C) 2012 Elsevier B.V. All rights reserved.