Nyengaard N, Vogensen F K, Josephsen J
Department of Dairy and Food Science, Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
Gene. 1995 May 19;157(1-2):13-8. doi: 10.1016/0378-1119(95)91235-r.
Several restriction-modification (R-M) systems have been identified in Lactococcus lactis. Most of the systems have been plasmid encoded and function as phage-resistance mechanisms. At least five different type-II R-M systems, LlaAI, LlaBI, LlaCI, LlaDI and LlaEI, were identified in isolates from a mixed Cheddar starter culture. LlaAI and LlaBI recognized the DNA sequences 5'- decreases GATC-3' and 5'-C decreases TRYAG-3', respectively. The genes coding for the LlaAI and LlaBI R-M systems have been cloned and sequenced. The LlaAI R-M system had two genes coding for methyltransferases (MTases) and one gene coding for a restriction endonuclease (ENase). The MTases showed high homology to the MTases from DpnII. The LlaBI R-M system had one gene coding for a MTase and one gene coding for an ENase.
在乳酸乳球菌中已鉴定出几种限制修饰（R-M）系统。大多数系统由质粒编码，并作为噬菌体抗性机制发挥作用。在一种混合切达干酪发酵剂培养物的分离物中鉴定出至少五种不同的II型R-M系统，即LlaAI、LlaBI、LlaCI、LlaDI和LlaEI。LlaAI和LlaBI分别识别DNA序列5'-decreases GATC-3'和5'-C decreases TRYAG-3'。编码LlaAI和LlaBI R-M系统的基因已被克隆和测序。LlaAI R-M系统有两个编码甲基转移酶（MTases）的基因和一个编码限制性内切酶（ENase）的基因。这些MTases与来自DpnII的MTases具有高度同源性。LlaBI R-M系统有一个编码MTase的基因和一个编码ENase的基因。
