Study On The Interaction Between DNA And DNA Topoisomerase Ⅰ From Mycobacterium Tuberculosis

DNA topoisomerase I (EC 5.99.1.2), a typeâ… topoisomerase, which is the important enzyme in accommodating and controlling the key life process of lives, is very necessary for the survival of biological cells. DNA topoisomeraseâ… cuts one strand of a DNA double helix, relaxation occurs, and then the cut strand is reannealed. And this process does not require energy cofactor, such as ATP or NAD. Because the first step to catalyze the relaxation reaction is the Topoâ… protein combining DNA, we started the research to the interaction of Mycobacterium tuberculosis topoisomeraseâ… (MTB Topoâ… ) and DNA in order to understand the binding mechanism of MTB Topoâ… and DNA. We made the research to the characteristics of the combination of MTB Topoâ… and DNA and discovered that:MTB Topoâ… can combine with both the double-stranded DNA and single-stranded DNA, as a single-stranded, double-stranded binding protein; MTB Topoâ… can combine with the DNA fragments with the strong topoisomerase binding sites (STS) sequences or not, in other words, MTB Topoâ… can combine DNA without thinking of if STS sequence exists or not. And the EMSA assays of MTB Topoâ… and double-strain DNA owns such features as binding to DNA instantaneously, High temperature resistance, independently to magnesium ion, moreover it adapts to adapted to the environmental conditions of neutral and acidic pH. On this foundation we also compared the characteristics of binding-DNA of MTB Topoâ… and E. coli Topoâ… ,E. coli Topoâ…¢, and the discovery is that MTB Topoâ… has a stronger DNA binding activity than the other two types of topoisomeraseâ… proteins. MTB Topoâ… can also be combined with yeast tRNA to speculate ir may be a RNA-binding protein.The concludes reveal that the enzyme has a relatively unique nature, and maybe play an irreplaceable role in the process of the DNA replication, transcription, and chromosome reorganization concentration. these research findings will also help to understand the MTB Topoâ… catalytic DNA topology change mechanism, described MTB Topoâ… in DNA binding mechanism, which can further explore the basic laws of life activities and MTB growth control mechanism, to find effective new drug targets and anti-tuberculosis drug resistance in the design of and screening new ideas, so as to promote the prevention of tuberculosis.