臺灣博碩士論文加值系統

醣體抑制蛋白 (Ribosome-inactivating Proteins；RIPs) 是一群可以很
獨特抑制真核細胞核醣體活性的蛋白，其很廣泛地存在植物界中。到目前
為止，有兩類這種核醣體抑制蛋白被發現：第一類均由單一多鏈(A
鏈)組成，多為鹼性醣蛋白，稱之為第一型RIPs(Type I RIPs)。第二類由
兩分子多鏈組成，由一分子與第一型RIPs 相似的多鏈以單一雙
硫鍵連接另一分子可結合到細胞膜表面半乳糖的多鏈 (B 鏈) 所組成
。在本實驗中，由準人瓜 (Sechium edule Swartz) 種子純化出一種蛋白
質，我們將之命名為 SECHIUMIN。經 SDS/PAGE 分析，發現 Sechiumin
由單一多鏈所構成，分子量約為 34,500 Dalton；由等電點焦集電
泳(IEF)分析及 PAS染色得知其等電點為 pH 8.4 而且是一醣蛋白。
Sechiumin 抑制非細胞系統蛋白生合成百分之五十的劑量 (IC50) 為 1
nM，遠低於抑制完整細胞蛋白生合成的 IC50 (5000-6000 nM)。將
Sechiumin 與老鼠肝臟抽出之核醣體一起反應，再以 Aniline 處理，由
含有 7M 尿素的丙烯醯板膠電泳分析，與其它RIPs一樣，可發現一特殊
的 RNA 片段被釋放出來。由以上這些結果，證實 Sechiumin 是一種新的
第一型RIPs。

Ribosome-inactivating proteins (RIPs) are a group of related
proteins that are widely distributed throughout the plant
kingdom and share an unusual property of being able to
inactivate eukaryotic ribosomes. A new type I ribosome-
inactivating protein was purified from the seeds of Sechium
edule Swartz by gel-filtration chromatography, ion exchange
chromatography with CM52 cellulose column and FPLC Mono S
column.The purified new type I RIP was designated as SECHIUMIN.
The homogeneity of sechiumin was shown by SDS/PAGE analysis and
the results indicated that sechiumin consists of a single
polypeptide chain with a molecular weight of about 34,500
Dalton. From the results of IEF analysis and PAS staining,
sechiumin was considered to be a basic (pI 8.4) glycoprotein.
This protein inhibited the protein synthesis of a rabbit
reticulocyte lysate with an IC50 (concentration causing 50%
inhibition) of 1 nM and had much less effect on protein
synthesis of Hela cells with IC50 of 5000-6000 nM. After rat
liver ribosomes were treated with 1 nM sechiumin, the total
rRNAs were isolated and treated with aniline, and a new rRNA
fragment could be clearly observed , just like other RIPs , by
PAGE. From these data, it was concluded that sechiumin is one
of the type I ribosome- inactivating proteins.