Ling J, Liu W Y, Wang T P
Shanghai Institute of Biochemistry, Academia Sinica, China.
Biochim Biophys Acta. 1995 Sep 27;1252(1):15-22. doi: 10.1016/0167-4838(95)00052-v.
Two types of ribosome-inactivating proteins (RIPs), camphorin and cinnamomin, have been purified from the seeds of Cinnamomum camphora. Camphorin is a type I RIP with a molecular mass of 23 kDa. Cinnamomin is a type II RIP having three isoforms, its molecular mass is around 61 kDa. The A- and B-chain derived from cinnamomin isoforms have similar mobilities in SDS-polyacrylamide gel. Camphorin and cinnamomin are both glycoproteins. In phylogenesis, it is particularly significant to find the simultaneous existence of type I and type II RIP as well as three isoforms of the latter in the same organ of a higher plant. The molecular mechanism of action of these two RIPs on mammalian ribosomes was demonstrated to be the specific RNA N-glycosidase activity. They modify 28S RNA among the four species of ribosomal RNAs. The cleavage site is the adenosine at position 4324 (rat liver 28S rRNA) embedded in the highly conserved 'R/S domain'. It is the first report that an intact type II RIP (cinnamomin) exhibits RNA N-glycosidase activity. Additionally, camphorin and cinnamomin can cleave supercoiled double-stranded DNA into nicked and linear forms (Ling et al. (1994) FEBS Lett. 345, 143-146).
已从樟树种子中纯化出两种核糖体失活蛋白（RIPs），即樟脑毒素和肉桂毒素。樟脑毒素是一种I型RIP，分子量为23 kDa。肉桂毒素是一种II型RIP，有三种同工型，分子量约为61 kDa。肉桂毒素同工型衍生的A链和B链在SDS-聚丙烯酰胺凝胶中具有相似的迁移率。樟脑毒素和肉桂毒素均为糖蛋白。在系统发育中，在高等植物的同一器官中同时存在I型和II型RIP以及后者的三种同工型具有特别重要的意义。这两种RIP对哺乳动物核糖体的分子作用机制被证明是特定的RNA N-糖苷酶活性。它们在四种核糖体RNA中修饰28S RNA。切割位点是位于高度保守的“R/S结构域”中的4324位腺苷（大鼠肝脏28S rRNA）。这是首次报道完整的II型RIP（肉桂毒素）具有RNA N-糖苷酶活性。此外，樟脑毒素和肉桂毒素可将超螺旋双链DNA切割成带切口的线性形式（Ling等人，（1994年）《欧洲生物化学学会联合会快报》345，143 - 146）。
