Wang P, Tumer N E
Biotechnology Center and the Department of Plant Pathology, Foran Hall, Room 208, Cook College,Rutgers University, Dudley Road, New Brunswick, NJ 08903, USA.
Nucleic Acids Res. 1999 Apr 15;27(8):1900-5. doi: 10.1093/nar/27.8.1900.
Ribosome-inactivating proteins (RIPs) are N-glycosylases that remove a specific adenine from the sarcin/ricin loop of the large rRNA in a manner analogous to N-glycosylases that are involved in DNA repair. Some RIPs have been reported to remove adenines from single-stranded DNA and cleave double-stranded supercoiled DNA. The molecular basis for the activity of RIPs on double-stranded DNA is not known. Pokeweed antiviral protein (PAP), a single-chain RIP from Phytolacca americana, cleaves supercoiled DNA into relaxed and linear forms. Double-stranded DNA treated with PAP contains apurinic/apyrimidinic (AP) sites due to the removal of adenine. Using an active-site mutant of PAP (PAPx) which does not depurinate rRNA, we present evidence that double-stranded DNA treated with PAPx does not contain AP sites and is not cleaved. These results demonstrate for the first time that PAP cleaves supercoiled double-stranded DNA using the same active site that is required for depurination of rRNA.
核糖体失活蛋白（RIPs）是一种N-糖苷酶，它以类似于参与DNA修复的N-糖苷酶的方式，从大核糖体RNA的肌动蛋白/蓖麻毒素环中去除特定的腺嘌呤。据报道，一些RIPs能从单链DNA中去除腺嘌呤，并切割双链超螺旋DNA。RIPs对双链DNA活性的分子基础尚不清楚。商陆抗病毒蛋白（PAP）是一种来自美洲商陆的单链RIP，它能将超螺旋DNA切割成松弛和线性形式。用PAP处理的双链DNA由于腺嘌呤的去除而含有无嘌呤/无嘧啶（AP）位点。使用不能使核糖体RNA脱嘌呤的PAP活性位点突变体（PAPx），我们提供证据表明，用PAPx处理的双链DNA不含有AP位点且未被切割。这些结果首次证明，PAP使用与核糖体RNA脱嘌呤所需相同的活性位点来切割超螺旋双链DNA。
