Xu F F, Pearce L E, Yu P L
Department of Biotechnology, Massey University, Palmerston North, New Zealand.
Mol Gen Genet. 1991 May;227(1):33-9. doi: 10.1007/BF00260703.
The sequence and genetic organization was determined of the 2508 bp lactococcal portion of pFX2, which was derived from a cryptic Lactococcus lactis subsp. lactis plasmid and used as the basis for construction of a series of lactococcal vectors. A lactococcal plasmid plus origin and two replication protein-coding regions (repA and repB) were located. RepA has a helix-turn-helix motif, a geometry typical of DNA-binding proteins. RepB shows a high degree of homology to the plasmid replication initiation proteins from other gram-positive bacteria and Mycoplasma. The transcribed inverted repeat sequence between repA and repB could form an attenuator to regulate pFX2 replication. Up-stream of the ori site, and in a region which was non-essential for replication, a 215 bp sequence identical to the staphylococcal plasmid pE194 and carrying the RSA site was identified. The genetic organization of this lactococcal plasmid replicon shares significant similarity with pE194 group plasmids.
测定了源自隐秘乳酸乳球菌亚种乳酸乳球菌质粒的pFX2的2508 bp乳球菌部分的序列和基因组织，并以此为基础构建了一系列乳球菌载体。定位了一个乳球菌质粒及其复制起点和两个复制蛋白编码区（repA和repB）。RepA具有螺旋-转角-螺旋基序，这是DNA结合蛋白的典型结构。RepB与其他革兰氏阳性菌和支原体的质粒复制起始蛋白具有高度同源性。repA和repB之间转录的反向重复序列可形成一个衰减子来调节pFX2的复制。在ori位点上游且对复制非必需的区域，鉴定出一个与葡萄球菌质粒pE194相同且携带RSA位点的215 bp序列。该乳球菌质粒复制子的基因组织与pE194族质粒具有显著相似性。
