Vujcic M, Topisirovic L
Institute of Molecular Genetics and Genetic Engineering, Belgrade, Yugoslavia.
Appl Environ Microbiol. 1993 Jan;59(1):274-80. doi: 10.1128/aem.59.1.274-280.1993.
Lactobacillus plantarum A112 has four different plasmids. Plus-origin-specific probes were used to determine that the smallest, cryptic plasmid, pA1 (2,820 bp), showed homology to the pE194 plasmid family. This subclass of plasmids uses the rolling-circle mode of replication. Subsequent analysis of plasmid pA1 demonstrated that it generates single-stranded DNA intermediates, and sequence analysis revealed that it contains three putative open reading frames (ORFs): ORF1, ORF2, and ORF3, which could encode proteins designated RepA (47 amino acids [aa]) and RepB (196 aa) and a protein of 103 aa, respectively. Two of these proteins, RepA (5.6 kDa) and RepB (26 kDa), were identified in in vitro transcription translation assays. The RepA protein contains a characteristic alpha-helix-turn-alpha-helix motif typical of DNA-binding proteins that act as DNA-binding repressors. The RepB protein shows a significant similarity with replication initiation proteins of the pE194 family of plasmids that use the rolling-circle mode of replication. Plasmid pA1 is able to replicate in Escherichia coli and Lactobacillus lactis subsp. lactis as well as in other L. plantarum strains.
植物乳杆菌A112有四种不同的质粒。使用正向原点特异性探针确定最小的隐蔽质粒pA1（2820 bp）与pE194质粒家族具有同源性。这类质粒采用滚环复制模式。随后对质粒pA1的分析表明它能产生单链DNA中间体，序列分析显示它含有三个推定的开放阅读框（ORF）：ORF1、ORF2和ORF3，它们分别可编码名为RepA（47个氨基酸[aa]）和RepB（196个aa）的蛋白质以及一个103个aa的蛋白质。其中两种蛋白质，RepA（5.6 kDa）和RepB（26 kDa），在体外转录翻译试验中得到了鉴定。RepA蛋白含有典型的α-螺旋-转角-α-螺旋基序，这是作为DNA结合阻遏物的DNA结合蛋白所特有的。RepB蛋白与采用滚环复制模式的pE194质粒家族的复制起始蛋白有显著相似性。质粒pA1能够在大肠杆菌、乳酸乳球菌乳酸亚种以及其他植物乳杆菌菌株中复制。
