THE PUTATIVE IMMUNITY PROTEIN OF THE GRAM-POSITIVE BACTERIA LEUCONOSTOC-MESENTEROIDES IS PREFERENTIALLY LOCATED IN THE CYTOPLASM COMPARTMENT

Immunity proteins are thought to protect bacteriocin-producing bacteri al strains against the bactericidal effects of their own bacteriocin. The immunity protein which protects the lactic acid bacterium Leuconos toc mesenteroides against mesentericin Y105(37) bacteriocin was detect ed and localized by immunofluorescence and electron microscopy, using antibodies directed against the C-terminal end of the predicted immuni ty protein. The antibodies recognized the immunity proteins of various strains of Leuconostoc, including Leuconostoc mesenteroides and Leuco nostoc gelidum. This study demonstrated that immunity proteins produce d by Leuconostoc mesenteroides accumulated in the cytoplasmic compartm ent of the bacteria. This is in contrast with other known immunity pro teins, such as the colicin immunity proteins, which are integral membr ane proteins possessing three to four transmembrane domains.