| 摘要 |
A type 1 topoisomerase, designated topoisomerase V, has been isolated and substantially purified from the halophilic thermophilic methanogen bacterium Methanopyrus kandleri. The topoisomerase was purified by a process including the steps of lysing cells of M. kandleri to form a lysate, treating the lysate with polyethyleneimine to form a precipitate and a supernatant, precipitating the polyethyleneimine supernatant with ammonium sulfate, chromatographing the ammonium sulfate precipitate on phosphocellulose to produce a phosphocellulose eluate, chromatographing the phosphocellulose eluate on heparin to produce a heparin eluate, and chromatographing the heparin eluate on a column capable of separating proteins by molecular size therein to produce a substantially purified thermostable DNA topoisomerase V. Topoisomerase V can relax DNA and can unlink DNA by reducing the linking number of closed circular DNA. Topoisomerase V is active over a wide range of temperatures and ionic conditions and does not require magnesium or ATP for its activity. It is recognized by anti-human topoisomerase I antibody. |
