Yang Zhi-cheng, Yang Lin, Zhang Ying-xia, Yu He-fen, An Wei
Department of Cell Biology, Capital Medical University, 10 You An Men Wai Xi Tou Tiao, Beijing, 100069, China.
Protein J. 2007 Aug;26(5):303-13. doi: 10.1007/s10930-007-9072-5.
Hepatic stimulator substance (HSS) is a novel liver-specific growth-promoting factor. Although HSS has been successfully crystallized, several properties of this protein have yet to be determined. This study shows that recombinant human HSS (rhHSS) is a dimer with a molecular mass of 31 kDa, the protein is weakly acidic and has an isoelectric point (pI) of 4.50. RhHSS was able to protect hepatoma cells from H2O2-induced apoptosis and to stimulate cell growth. The recombinant protein was thermostable up to 80 degrees C and resistant to changes in pH, as determined by synchronous fluorescence and far-UV circular dichroism (CD). Within the range of pH 4.0-10.0, rhHSS assumed a folded conformation identical to the secondary structure of the original, native protein and a native-like far-UV CD spectrum. Denatured rhHSS could be partly reconstituted with respect to its structure, but not its activity. Thus, rhHSS is a structurally stable protein insensitive to thermal and acid-alkaline denaturation.
肝刺激物质（HSS）是一种新型的肝脏特异性促生长因子。尽管HSS已成功结晶，但该蛋白质的一些特性尚未确定。本研究表明，重组人HSS（rhHSS）是一种分子量为31 kDa的二聚体，该蛋白质呈弱酸性，等电点（pI）为4.50。RhHSS能够保护肝癌细胞免受H2O2诱导的凋亡并刺激细胞生长。通过同步荧光和远紫外圆二色性（CD）测定，重组蛋白在高达80摄氏度时具有热稳定性，并且对pH变化具有抗性。在pH 4.0 - 10.0范围内，rhHSS呈现出与原始天然蛋白质二级结构相同的折叠构象以及类似天然的远紫外CD光谱。变性的rhHSS在结构上可以部分重构，但其活性不能重构。因此，rhHSS是一种对热变性和酸碱变性不敏感的结构稳定蛋白质。
