摘要
本文报道大肠杆菌的ColE1类似质粒的一个低拷贝数突变型。从载体质粒pUC4衍生的重组质粒pPGVT3在大肠杆菌宿主DF2145中是不稳定的,以pPGVT3转化DF2145时在4o℃培养得不到转化子。用诱发点突变的羟胺体外处理pPGVF3质粒DNA,得到一个稳定性提高了的突变质粒pPGVT3HA,突变的位置被确定在质粒的pUC部分,突变降低了pUC及其衍生质粒的拷贝数。文中对质粒的稳定性与拷贝数的关系作了讨论。
A low copy number mutant of CoIE1-like plasm id of Escherichia coli was reported in this paper.The recombinant plasmid pPGVT3 derived from the vector pUC4 was unstable in the E.coli host strain DF2145.No transformant could be obtained at 40℃ when DF2145 was transformed with pPGVT3.By in vitro mutagenesis of pPGVT3 plasmid DNA with hydroxylamine which induces point mutations,a mutant plasmid pPGVT3HA was obtained,which was stable in DE2145.The mutation site was localized within the pUC moiety of pPGVT3HA.The copy number of the mutated pUC vector and its derivatives were found to be reduced.The effect of low copy number mutation on the stability of the recombinant plasmids was discussed.