Studies on The Supercondensed pBR322 DNA Isolated From Escherichia coli topA-Mutant
- VernacularTitle:大肠杆菌topA-菌株中质粒pBR322的超凝集结构
- Author:
Zhenfeng ZHANG
;
Jia YU
;
Kou CAO
;
Xitai HUANG
- Publication Type:Journal Article
- Keywords:
suercondensed DNA, E. coli DM800, atomic force microscope, topoisomerase Ⅳ
- From:
Progress in Biochemistry and Biophysics
2006;0(03):-
- CountryChina
- Language:Chinese
-
Abstract:
The supercondensed DNA, a special kind of topological structure of plasmid DNA, was firstly found in E. coli SD108(topA+ gyrB225). Now, this structure is also found in E. coli DM800(topA- gyrB225). The result indicates that the formation of supercondensed DNA is related with decrease of the activity of gyrase in vivo. Topoisomerase Ⅳ was proved to relax the supercondensed DNA completely in vitro, which suggested that the supercondensed DNA and the supercoiled DNA could transform to each other in cells. The supercondensed DNA samples were analyzed by atomic force microscopy and compared to supercoiled DNA. The results showed that the length of supercondensed DNA decreased about 30% and the width and height of double-strand increased about 60%, which indicates that the structure of double-strand of supercondensed DNA is much more similar to A-DNA than B-DNA. The results also showed that chloroquine intercalation did not change the supercoiling level of supercondensed DNA, but made it knot and compact.
