由DNA连接酶催化的依赖AMP的DNA松弛通过切口封闭机制发生。

Montecucco A, Ciarrocchi G

Istituto di Genetica Biochimica ed Evoluzionistica, CNR, Pavia, Italy.

Nucleic Acids Res. 1988 Aug 11;16(15):7369-81. doi: 10.1093/nar/16.15.7369.

In the presence of AMP and Mg2+, a covalently closed duplex DNA containing negative superhelical turns was treated with DNA ligase isolated from bacteriophage T4-infected E. coli. This resulted in the gradual and not sudden loss of superhelical turns as for example in the case of type I DNA topoisomerase. All DNA products remain covalently closed. Since T4 enzyme-mediated DNA relaxation is inhibited by both pyrophosphate and by ATP this suggests that DNA relaxing and DNA joining activities probably coincide. EDTA addition in the presence of a large excess of enzyme, induces the formation of nicked DNA products while protein denaturing treatments are not very effective. Our observations might suggest an involvement of the relaxing activity of DNA ligase during the ligation process.

在存在AMP和Mg2+的情况下，用从噬菌体T4感染的大肠杆菌中分离出的DNA连接酶处理含有负超螺旋圈的共价闭合双链DNA。这导致超螺旋圈逐渐而非突然丢失，例如在I型DNA拓扑异构酶的情况下。所有DNA产物仍保持共价闭合。由于T4酶介导的DNA松弛受到焦磷酸和ATP的抑制，这表明DNA松弛和DNA连接活性可能是一致的。在存在大量过量酶的情况下添加EDTA会诱导切口DNA产物的形成，而蛋白质变性处理效果不太显著。我们的观察结果可能表明DNA连接酶的松弛活性在连接过程中起作用。