Physiological role of neonatal brain-derived carcinostatic factor(NBCF) during the ontogenesis

小鼠脑在新生期而不是在成体或胎儿期分泌一种蛋白质，其优先抑制恶性细胞的生长和DNA合成而不是正常细胞的生长和DNA合成，因此被称为新生儿脑源性抑癌因子（NBCF）。在本研究中，NBCF是从新生儿脑培养的条件培养基中制备的，并且通过HPLC获得为均质蛋白（62 kDa，PI 9.1）; NBCF的物理化学和生物学性质不同于已知的脑蛋白。1，2-顺式二醇亲和柱保留NBCF，其后用D-山梨醇洗脱;用神经氨酸酶处理的NBCF失去了部分活性，而没有出现新的N-末端氨基酸，表明活性展览所需的聚糖部分。这得到了衣霉素（剂量低至无细胞毒性）抑制NBCF分泌的支持。NBCF不水解靶蛋白; NBCF的细胞毒性作用不被多种蛋白酶抑制剂抵消。NBCF的醚提取物没有细胞毒性，而醚不溶性残留物保留了部分初始活性。固定化胰蛋白酶或二硫苏糖醇与胍的组合灭活NBCF比任何一种试剂都更显着。因此，NBCF的细胞毒性展览，介导的行动以外的蛋白水解，是由于蛋白质的原则，但不是蛋白质结合的亲脂性配体，并需要保留的蛋白质构象和分子内埋SS键。

The mouse brain, at the neonatal stage but not at the adult or fetal stage, secretes a protein, which inhibits growth and DNA synthesis of malignant cells preferentially over those of normal cells, and so is termed neonatal brain-derived carcino- static factor (NBCF). In the present study NBCF was prepared from conditioned medium of the neonatal brain cultured, and was obtained by HPLC as a homogeneous protein (62 kDa, PI 9.1); physics-chemical and biological properties of NBCF differ from those of cerebral proteins known. A 1,2-cis-diol affinity column retained NBCF, which was thereafter eluted with D-sorbitol; NBCF treated with neuraminidase lost part of activity without emergence of new N-terminal amino acids, suggesting glycan moieties required for the activity exhibition. This is supported by repression of NBCF secretion by tunicamycin of doses as low as is not cytotoxic. NBCF did not hydrolize target proteins; cytotoxic action of NBCF was not counteracted by a diversity of protease inhibitors. An ether-extract of NBCF was not cytotoxic whereas the ether-insoluble residuum retained part of the initial activity. NBCF was inactivated with immobilized trypsin or with dithiothreitol combined with guanidine more markedly than with either agent. Thus cytotoxicity exhibition of NBCF, mediated through actions other than proteolysis, is attributed to the proteinic principle but not to protein-bound lipophilic ligands, and requires retention of the protein conformation and intramolecularly buried SS bonds.