Holo H, Nilssen O, Nes I F
Laboratory of Microbial Gene Technology, Oslo, Norway.
J Bacteriol. 1991 Jun;173(12):3879-87. doi: 10.1128/jb.173.12.3879-3887.1991.
A new bacteriocin, termed lactococcin A (LCN-A), from Lactococcus lactis subsp. cremoris LMG 2130 was purified and sequenced. The polypeptide contained no unusual amino acids and showed no significant sequence similarity to other known proteins. Only lactococci were killed by the bacteriocin. Of more than 120 L. lactis strains tested, only 1 was found resistant to LCN-A. The most sensitive strain tested, L. lactis subsp. cremoris NCDO 1198, was inhibited by 7 pM LCN-A. By use of a synthetic DNA probe, lcnA was found to be located on a 55-kb plasmid. The lcnA gene was cloned and sequenced. The sequence data revealed that LCN-A is ribosomally synthesized as a 75-amino-acid precursor including a 21-amino-acid N-terminal extension. An open reading frame encoding a 98-amino-acid polypeptide was found downstream of and in the same operon as lcnA. We propose that this open reading frame encodes an immunity function for LCN-A. In Escherichia coli lcnA did not cause an LCN-A+ phenotype. L. lactis subsp. lactis IL 1403 produced small amounts of the bacteriocin and became resistant to LCN-A after transformation with a recombinant plasmid carrying lcnA. The other lactococcal strains transformed with the same recombinant plasmid became resistant to LCN-A but did not produce any detectable amount of the bacteriocin.
从乳酸乳球菌乳脂亚种LMG 2130中纯化并测序得到了一种新的细菌素，命名为乳球菌素A（LCN-A）。该多肽不含有异常氨基酸，且与其他已知蛋白质没有显著的序列相似性。只有乳球菌会被这种细菌素杀死。在测试的120多种乳酸乳球菌菌株中，仅发现1株对LCN-A具有抗性。测试中最敏感的菌株，即乳酸乳球菌乳脂亚种NCDO 1198，会被7 pM的LCN-A抑制。通过使用合成DNA探针，发现lcnA位于一个55 kb的质粒上。lcnA基因被克隆并测序。序列数据显示，LCN-A作为一种75个氨基酸的前体通过核糖体合成，包括一个21个氨基酸的N端延伸。在lcnA下游且与其在同一个操纵子中发现了一个编码98个氨基酸多肽的开放阅读框。我们推测这个开放阅读框编码LCN-A的免疫功能。在大肠杆菌中，lcnA不会导致LCN-A+表型。乳酸乳球菌乳酸亚种IL 1403产生少量细菌素，在用携带lcnA的重组质粒转化后对LCN-A产生抗性。用相同重组质粒转化的其他乳球菌菌株对LCN-A产生抗性，但未产生任何可检测量的细菌素。
