DNA topoisomerase I was partially purified from Caenorhabditis elegans worms. The enzyme is a 95 kDa polypeptide and its proteolytically degraded form of 70 kDa was also observed. The enzyme removed not only negative but also positive DNA supercoils. The optimum salt concentration for the DNA relaxation activity was 100 mM KCl, and divalent cations were not required but stimulated the activity. The DNA relaxation activity was weakly sensitive to 125 μM camptothecin but was completely inhibited by 125 μM berenil.
Bibliographical noteFunding Information:
We thank Dr. Nam Jeong Cho (Chungbuk National University, Republic of Korea) for giving us C. elegans N2 and E. coli OP50. We are grateful to Drs. Leroy F. Liu and Peter D'Arpa (University of Medicine and Dentistry at New Jersey) for sending us rabbit antiserum against calf thymus DNA topoisomerase I. This work was supported by a Genetic Engineering Research Grant from the Ministry of Education, Korea.
All Science Journal Classification (ASJC) codes
- Structural Biology