Nie H, Cai X, He X, Xu L, Ke X, Ke Y, Tam S C
Shanghai Institute of Cell Biology, Academia Sinica, China.
Life Sci. 1998;62(6):491-500. doi: 10.1016/s0024-3205(97)01145-4.
Trichosanthin (TCS) is a type-I ribosome-inactivating protein (RIP) with wide spectrum of biological and pharmacological activities. In the present study, a potential site on the TCS molecule (position 120-123) is identified which may be important for the biological activities of TCS. By using site-directed mutagenesis, position 120-123 of TCS was either deleted or changed from Lys-Ile-Arg-Glu (hydrophilic) to Ser-Ala-Gly-Gly (hydrophobic). Deletion of these residues rendered a TCS molecule completely deprived of ribosome inactivating activity, while hydrophobic replacement caused 4000-fold decrease in ribosome inactivating activity. The abortifacient activity of these two mutants was retained with decreased potency. This implies that position 120-123 of the native TCS molecule plays a critical role in maintaining its biological activity.
天花粉蛋白（TCS）是一种I型核糖体失活蛋白（RIP），具有广泛的生物学和药理活性。在本研究中，确定了TCS分子上的一个潜在位点（第120 - 123位），该位点可能对TCS的生物学活性很重要。通过定点诱变，TCS的第120 - 123位要么被删除，要么从赖氨酸 - 异亮氨酸 - 精氨酸 - 谷氨酸（亲水）变为丝氨酸 - 丙氨酸 - 甘氨酸 - 甘氨酸（疏水）。删除这些残基使TCS分子完全丧失核糖体失活活性，而疏水取代导致核糖体失活活性降低4000倍。这两个突变体的堕胎活性得以保留，但效力降低。这意味着天然TCS分子的第120 - 123位在维持其生物学活性中起关键作用。
