title: Crystal structure and mutagenic analysis of a bacteriocin immunity protein, Mun-im.
abstract: Bacteriocin-producing lactic acid bacteria (LAB) possess a self-protection factor, which is generally called an immunity protein. In this study, we determine the crystal structure of an immunity protein, designated Mun-im, which was classified into subgroup B immunity proteins for class IIa bacteriocins. The Mun-im protein takes a left-turning antiparallel four-helix bundle structure with the flexible N- and C-terminal parts. Although the amino acid sequences of the subgroup B immunity proteins are distinguished from those of the subgroup A, the core structure of Mun-im is well-superimposed with that of the subgroup A immunity protein, EntA-im, and the C-terminus of both proteins is flexible. However, the C-terminus of Mun-im is obviously shorter than that of the subgroup A. We found through mutagenic study of Mun-im that the C-terminus and the K86 residue on the helix 4 in the immunity protein molecule are important for expression of the immunity activity on the subgroup B immunity proteins.
authors.affiliation: Department of Molecular Microbiology and Biotechnology, Graduate School of Biomedical Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551, Japan.
authors.forename: Hyung Joon
authors.initials: HJ
authors.lastname: Jeon
authors.forename: Masafumi
authors.initials: M
authors.lastname: Noda
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Matoba
authors.forename: Takanori
authors.initials: T
authors.lastname: Kumagai
authors.forename: Masanori
authors.initials: M
authors.lastname: Sugiyama
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D001430:Bacteriocins / Q000276:immunology*; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D016983:Enterococcus / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008969:Molecular Sequence Data; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; D001430:Bacteriocins