1. Key Laboratory of Cellular and Molecular Evolution, Kunming Institute of Zoology, the Chinese Academy of Sciences, Kunming 650223, China; 2. Graduate School of the Chinese Academy of Sciences, Beijing 100049, China; 3. Yunnan Key Laboratory of Molecular Biology of Domestic Animals, Kunming Institute of Zoology, the Chinese Academy of Sciences, Kunming 650223, China
DNA strand scission and topology changes are catalyzed by DNA topoisomerases. Previous studies suggest that Type ⅡB topoisomerase evolved from Type ⅡA by gene duplication, recombination and absence. However, this study shows that the evolutionary relationship between Type ⅠA and ⅡB is closer than that between Type ⅡA and ⅡB. Thus, Type ⅡB is possibly from Type ⅠA, or Type ⅡB is a special form of ⅠA in archaebacteria; Type ⅡB is probably evolved from ⅡA via ⅠA rather than from ⅡA directly. During the evolution of ⅡA to ⅡB via ⅠA, the catalytic mechanisms of DNA topoisomerases have also been changed; that is, metal ions are necessary in the catalyses for both ⅠA and ⅡA, but no ion is needed for ⅡB.
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