小鼠肝脏免疫抑制蛋白质(LISP)的分离纯化和鉴定

用硫酸铵分段盐析及DEAE-Sephadex A-50、羟磷灰石和CM纤维素等多种柱层析方法,从正常小鼠肝浸液中分离纯化出一种免疫抑制蛋白质(LISP)。在体外用微量该蛋白质就能强烈抑制小鼠T、B淋巴细胞对促有丝分裂原和同种异型抗原的增生反应。纯化的蛋白质在聚丙烯酰胺凝胶电泳(PACE)和等电聚焦(IEF)鉴定时均显示为一条区带,其等电点(pI)值在7.5—7.8范围。沉降系数利S_(20),w为5.39。Sephadex G-100凝胶层析测得LISP的分子量为78,000道尔顿。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)提示LISP是由二个相同的亚基组成,亚基分子量为38,500道尔顿。LISP是一种既非糖蛋白又非脂蛋白的碱性蛋白质,对它的氨基酸组成也作了分析。

Purification and Characterization of Murine Liver Immunosuppressive Protein

The liver immunosuppressive protein (LISP) was isolated and purified from murine liver extract by the use of ammonium sulfate fractionation and chromato graphy successively with DEAE-Sephadex A-50, hydroxylapatite and CM cellulose columns. The purified protein contained no detectable carbohydrate or lipid and appeared to be homogeneou as identified by polyacrylamide gel electrophoresis (PAGE) and isoelectric focusing (IEF) . The molecular weight of purified LISP was determined by gel filtration on Sephadex G-100 to be 78000 daltons and by SDS-PAGE to be 38500 daltons. These results indicate that each molecule of LISP is a dimer consisting of two identical subunits. The PI is in the range of 7.5 to 7.8.S20,w is 5.39. The specific lymphocyte inhibiting activity of the purified protein is less than 0.3 βg per culture. LISP is distinct from other liver inhibitory proteins.