State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences^* Department of Chemistry, Graduate Programs of Biotechnology, Chemistry and Materials Science, University of Alabama in Huntsville^**
○Minghuang Chen^* Xiaomin Hou^* Qi Peng^* Feng Yang^* Liqing Chen^** Mingdong Huang^*

Trichosanthin (TCS) is a type 1 Ribosome inactivity protein which was first isolated from the root tuber of Trichosanthe kirilowii Maxim and crystallized by Chinese scientists. TCS has been crystallized from barbital buffer, using NaNO₃ as precipitant, the crystals belong to space group C2 with cell parameters a=75.60 Å, b=75.44 Å, c=88.36 Å, β=99.50°. TCS has also been crystallized from citrate buffer with KCl as precipitant, the crystals belong to space group P2₁2₁2₁ with cell parameters a=38.305 Å, b=76.225 Å, c=79.213 Å. Crystalline TCS has multiple pharmacological properties including abortifacent, anti-tumor and anti-HIV. When the crystallized TCS was further purified using Mono-S column, two distinct protein peaks were designated as α- and β-TCS according to the reverse order of elution from the Mono-S column, the minor peak was labelled β-TCS, which had an area less than 20% in total. Both α- and β-TCS showed a single band with an apparent molecular weight of 27 kDa by SDS-PAGE. ESI-MS analysis indicated that the molecular weight of β-TCS is 27143 Da， slightly less than that of α-TCS, 27167 Da. Highly purified β-TCS has been crystallized using KCl as precipitant. The crystals belong to space group P2₁2₁2₁ with cell parameters a=38.244 Å, b=86.934 Å, and c=135.785 Å, and have two molecules in the asymmetric unit. A data set to 1.6 Å resolution was collected with synchrotron source. We are grateful for financial support from NSFC (No.39970872) and NSF of Fujian Province (C97052).