为研究中药有效成分天花粉蛋白质(TCS)与苦瓜子蛋白质(MMC)的生物学活性，以 细胞遗传物质DNA为底物，经分子生物学技术分析，发现超盘旋双链DNA发生解旋和链结，单链 DNA发生断链，在合适条件下，已解旋和断链的分子还可重新盘绕，再成超盘旋，极微量的蛋白质 即表现出很强的作用。这一活性与1型DNA拓扑异构酶相同。

Trichosanthin (TCS)and mommorcharin(MMC)are ingradients of Tianhuafen and Kuguazi respectively of Chinese traditional medicinal materials. `TCS has been used clinically for inducing abortion. Recently their antitumor and antivirus activities were also reported. Especially the inhibition of HIV RNA in the cultured cells and the experimental treatment of AIDS with TCS had shed lights on the po-tential of Chinese medicinal materials to block HIV infection both in HIV carriers and AIDS patients. The MMC has the same characteristics as TCS.They all belong to the ribosome inactivating proteins (RIP) and perform ribonucleosidase activities similar to ricin. We found that the supercoiled double strand DNA couldbe decpiralized and catenated by TCS and MMC. While in optimal conditions the rcoiled conformation of the relaxed unfavorable DNA could be reconstructed by TCS and MMC. During treatment of super DNA with TCS or MMC in conditions eg. in PBS or incubated at lower temperature the despiralization of DNA was the main display in agarose electrophoresis. While in the optimal conditions the catenation of DNA appeared in addition to the dispiralizarion. Sometimes all the DNA molecules became despiralized and catenated even with only 2~5ng of TCS or MMC. This reaction was independent of ATP. The EDTANa2 and DTT in the reactant was beneficial to the reconstruction of supercoiled configuration of the despiralized DNA. Based on the action of alteration of DNA configuration it was considered that these activities are similar to type 1 DNA topoiso- merase.

国家自然科学基金 No39470218