Siegers K, Entian K D
Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany.
Appl Environ Microbiol. 1995 Mar;61(3):1082-9. doi: 10.1128/aem.61.3.1082-1089.1995.
The lantibiotic nisin is produced by several strains of Lactococcus lactis. The complete gene cluster for nisin biosynthesis in L. lactis 6F3 comprises 15 kb of DNA. As described previously, the structural gene nisA is followed by the genes nisB, nisT, nisC, nisI, nisP, nisR, and nisK. Further analysis revealed three additional open reading frames, nisF, nisE, and nisG, adjacent to nisK. Approximately 1 kb downstream of the nisG gene, three open reading frames in the opposite orientation have been identified. One of the reading frames, sacR, belongs to the sucrose operon, indicating that all genes belonging to the nisin gene cluster of L. lactis 6F3 have now been identified. Proteins NisF and NisE show strong homology to members of the family of ATP-binding cassette (ABC) transporters, and nisG encodes a hydrophobic protein which might act similarly to the immunity proteins described for several colicins. Gene disruption mutants carrying mutations in the genes nisF, nisE, and nisG were still able to produce nisin. However, in comparison with the wild-type strain, these mutants were more sensitive to nisin. This indicates that besides nisI the newly identified genes are also involved in immunity to nisin. The NisF-NisE ABC transporter is homologous to an ABC transporter of Bacillus subtilis and the MbcF-MbcE transporter of Escherichia coli, which are involved in immunity to subtilin and microcin B17, respectively.
羊毛硫抗生素乳链菌肽由几种乳酸乳球菌菌株产生。乳酸乳球菌6F3中乳链菌肽生物合成的完整基因簇包含15 kb的DNA。如前所述，结构基因nisA后面跟着基因nisB、nisT、nisC、nisI、nisP、nisR和nisK。进一步分析发现，在nisK附近还有另外三个开放阅读框，即nisF、nisE和nisG。在nisG基因下游约1 kb处，已鉴定出三个方向相反的开放阅读框。其中一个阅读框sacR属于蔗糖操纵子，这表明乳酸乳球菌6F3中属于乳链菌肽基因簇的所有基因现已被鉴定出来。蛋白质NisF和NisE与ATP结合盒（ABC）转运蛋白家族的成员具有很强的同源性，nisG编码一种疏水蛋白，其作用可能类似于几种大肠杆菌素所描述的免疫蛋白。在基因nisF、nisE和nisG中携带突变的基因破坏突变体仍然能够产生乳链菌肽。然而，与野生型菌株相比，这些突变体对乳链菌肽更敏感。这表明除了nisI外，新鉴定的基因也参与了对乳链菌肽的免疫。NisF-NisE ABC转运蛋白与枯草芽孢杆菌的一种ABC转运蛋白以及大肠杆菌的MbcF-MbcE转运蛋白同源，它们分别参与对枯草菌素和微菌素B17的免疫。
