Darabi A, Forough R, Bhardwaj G, Watabe M, Goodarzi G, Gross S C, Watabe K
Department of Medical Microbiology/Immunology, Southern Illinois University School of Medicine, Springfield 62708.
Plasmid. 1989 Nov;22(3):281-6. doi: 10.1016/0147-619x(89)90015-2.
The plasmid pBS2 has a low copy number and is endogenous to Bacillus subtilis. The replication of this plasmid depends on the function of most of the host's dna genes including dnaB, which is unique to B. subtilis and is required for both the initiation of chromosome replication and the DNA-membrane association. We have identified the region that is essential for the replication of pBS2 and determined the complete 2279-bp nucleotide sequence of this region. In this region, there are two stretches of sequence homologous to the 18-bp consensus sequence which commonly appears at the origin of replication of plasmids pUB110 and pC194. The entire region contains six sizable open reading frames. Two of them are probably translated. One open reading frame, designated ORF A, coding for 269 amino acids, has significant homology, in terms of amino acid sequence, with the open reading frame of the gene for the Rep U protein of plasmid pUB110. The similarities between pBS2 and other plasmids suggest that the pBS2 may also replicate as a rolling circle, which appears to be the salient feature of a mechanism of replication that is common to small plasmids in gram-positive bacteria.
质粒pBS2拷贝数低，是枯草芽孢杆菌的内源质粒。该质粒的复制依赖于宿主大多数dna基因的功能，包括dnaB，它是枯草芽孢杆菌特有的，对染色体复制起始和DNA与膜的结合均是必需的。我们已鉴定出对pBS2复制至关重要的区域，并确定了该区域完整的2279碱基对核苷酸序列。在该区域，有两段与18碱基共有序列同源的序列，该共有序列常见于质粒pUB110和pC194的复制起点。整个区域包含六个相当大的开放阅读框。其中两个可能被翻译。一个开放阅读框，命名为ORF A，编码269个氨基酸，就氨基酸序列而言，与质粒pUB110的Rep U蛋白基因的开放阅读框有显著同源性。pBS2与其他质粒之间的相似性表明，pBS2也可能以滚环方式复制，这似乎是革兰氏阳性菌中小质粒常见的一种复制机制的显著特征。
