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通过硫酸铵分级沉淀、ＣＭ－５２阳离子交换层析、ＨＲＬＣ分子排阻层析及ＦＰＬＣＭｏｎｏＳ离子交换层析等步骤，从丝瓜籽中分离到一组分子量为８ｋＤ左右的小分子核糖体失活蛋白——ＬｕｆｉｎＳ１、ＬｕｆｉｎＳ２、ＬｕｆｉｎＳ３。末端分析结果表明，它们的Ｎ端氨基酸分别为Ａｌａ、Ｐｒｏ和Ｔｈｒ。氨基酸序列分析确定了ＬｕｆｉｎＳ２的Ｎ端９个氨基酸的序列是Ｐｒｏ－Ａｒｇ－Ａｒｇ－Ｇｌｙ－Ｇｌｎ－Ｇｌｕ－Ａｌａ－Ｐｈｅ－Ａｓｐ。ＬｕｆｉｎＳｓ对核糖体的失活机制与天花粉蛋白（ＴＣＳ）一致，是ＲＮＡＮ－糖苷酶催化型的。它们对无细胞蛋白质生物合成的抑制活性较ＴＣＳ略强，ＩＣ５０分别为１．３×１０－１１、１．０×１０－１０和６．３×１０－１１ｍｏｌ／Ｌ左右。因此ＬｕｆｉｎＳｓ有可能开发成免疫毒素的高效“弹头”。
A group of small molecule ribosome inactivating protein with a molecular weight of about 8 kD was isolated from the loofah seeds by ammonium sulfate fractionation, CM-52 cation exchange chromatography, HRLC molecular exclusion chromatography and FPLCMonoS ion exchange chromatography, -LufinS1, LufinS2, LufinS3. Terminal analysis showed that their N-terminal amino acids were Ala, Pro and Thr, respectively. Amino acid sequence analysis confirmed that the N-terminal 9 amino acid sequence of LufinS2 was Pro-Arg-Arg-Gly-Gln-Glu-Ala-Phe-Asp. The mechanism of inactivation of ribosomes by LufinSs is consistent with trichosanthin (TCS) and is RNAN-glycosidase-catalyzed. Their inhibitory activity on cell-free protein biosynthesis is slightly stronger than TCS with IC50 of 1.3 × 10-11, 1.0 × 10-10 and 6.3 × 10-11mol / L, respectively. LufinSs is therefore likely to develop an efficient “warhead” of immunotoxins.