Zhang Y, Praszkier J, Hodgson A, Pittard A J
Department of Microbiology, University of Melbourne, Parkville, Victoria, Australia.
J Bacteriol. 1994 Sep;176(18):5718-28. doi: 10.1128/jb.176.18.5718-5728.1994.
Plasmid pEP2 was found to encode a protein, RepA, which is essential and rate limiting for its replication in Escherichia coli and Corynebacterium pseudotuberculosis. Mutations which altered the rate of synthesis of this protein in E. coli affected the copy number and segregational stability of pEP2 in the two hosts. RepA contains 483 amino acid residues and has the calculated molecular weight of 53,925. It shows 45% amino acid residue identity with open reading frame ORF2 of pSR1, a plasmid isolated from Corynebacterium glutamicum (J. A. C. Archer and A. J. Sinskey, J. Gen. Microbiol. 139:1753-1759, 1993). Plasmid pEP2 was shown to accumulate single-stranded DNA corresponding to the RepA coding strand during its replication in E. coli and C. pseudotuberculosis, suggesting that it may replicate by a rolling circle mechanism. However, RepA has no significant sequence homology with the replication initiator proteins of plasmids known to use this mode of replication.
发现质粒pEP2编码一种蛋白质RepA，它对其在大肠杆菌和假结核棒状杆菌中的复制至关重要且是限速的。在大肠杆菌中改变该蛋白质合成速率的突变影响了pEP2在这两种宿主中的拷贝数和分离稳定性。RepA含有483个氨基酸残基，计算分子量为53,925。它与从谷氨酸棒状杆菌分离的质粒pSR1的开放阅读框ORF2有45%的氨基酸残基同一性（J. A. C. Archer和A. J. Sinskey，《普通微生物学杂志》139:1753 - 1759，1993）。在大肠杆菌和假结核棒状杆菌中复制期间，质粒pEP2被证明会积累与RepA编码链对应的单链DNA，这表明它可能通过滚环机制进行复制。然而，RepA与已知使用这种复制模式的质粒的复制起始蛋白没有显著的序列同源性。
