Zhang N, Brooker J D
Animal Sciences Department, Waite Agricultural Research Institute, University of Adelaide, Australia.
Plasmid. 1993 Mar;29(2):125-34. doi: 10.1006/plas.1993.1014.
A 2.5-kb cryptic plasmid, pJDB21, from the gram-negative ruminal anaerobe, Selenomonas ruminantium subspecies lactilytica, was mapped and sequenced. Five open reading frames (ORFs) were predicted and expression of two ORFs was demonstrated. Analysis of the predicted amino acid sequence of the ORF 1 protein indicated approximately 30% homology with the replication protein (rep) common to many gram-positive plasmids, and a highly conserved sequence representing the origin of replication in these plasmids was located upstream of ORF 1. This finding was consistent with a rolling circle form of replication for pJDB21. Transformation of Escherichia coli K-12 UB1636pol Ats with pJDB21 showed that the plasmid replicated independently of DNA polymerase I and produced a single-stranded DNA intermediate. Deletion analyses localized the E. coli replication function to a 1.4-kb sequence that was mapped to the predicted rep gene.
对来自革兰氏阴性瘤胃厌氧菌乳酸栖瘤胃月形单胞菌（Selenomonas ruminantium subspecies lactilytica）的一个2.5kb隐蔽质粒pJDB21进行了图谱绘制和测序。预测出五个开放阅读框（ORF），并证实了其中两个ORF的表达。对ORF1蛋白预测的氨基酸序列分析表明，其与许多革兰氏阳性质粒共有的复制蛋白（rep）具有约30%的同源性，并且在ORF1上游定位到了代表这些质粒复制起点的高度保守序列。这一发现与pJDB21的滚环复制形式一致。用pJDB21转化大肠杆菌K-12 UB1636pol Ats表明，该质粒独立于DNA聚合酶I进行复制，并产生单链DNA中间体。缺失分析将大肠杆菌的复制功能定位到一个1.4kb的序列上，该序列被定位到预测的rep基因上。
