Structure and complement activating activity of human serum mannan-binding protein

人血清甘露聚糖结合蛋白(MBP)是一种凝集素(糖类结合蛋白)，最先由这些作者描述。凝集素被证明具有激活补体的能力和直接调色素的功能，导致了凝集素是一种与自卫机制相关的新成分的概念。本研究对凝集素的结构、功能关系，特别是其补体激活活性进行了研究，主要结果如下：1)对人血清MBP的氨基酸序列进行了蛋白质化学研究。凝集素被还原和烷基化后，用赖氨酸内肽酶消化。2)以大鼠血清MBP c DNA为探针，从人肝cdna文库中克隆人血清MBP c DNA，用…方法测定其核苷酸序列。更多的脱氧终止方法。通过比较1)和2)中的结果，发现人血清MBP由248个氨基酸组成。3)血清MBP的大体结构与补体成分Clq非常相似。这促使我们研究血清MBP激活补体的分子机制。使用其他补体成分Clr和Cls的研究表明，血清MBP一旦与固相配体结合，就会与Clr*Cls补体联系在一起。在这个复合体上，Clr*CLS从酶原形式转化为激活的丝氨酸蛋白酶，导致补体系统经典途径的一系列级联反应的激活。4)血清MBP被证明对核心结构上含有半抗原糖(甘露糖、N乙酰氨基葡萄糖)的大肠杆菌K12、B菌株具有补体依赖性杀菌活性，对表面具有高甘露糖型寡糖链的培养哺乳动物细胞也具有细胞毒活性。较少

Human serum mannan-binding protein (MBP) is a lectin (carbohydrate binding protein), which was first described by these authors. The lectin has been shown to have the ability to activate complement and also to function as direct opsonin, leading to the concept that the lectin is a novel component associated with selfdefense mechanism. This study was undertaken to examine the structure function relationship particularly on its complement activating activity of the lectin with the results described below.1) Amino acid sequence of the human serum MBP was studied protein chemically. The lectin, which had been reduced and alkylated, was digested with lysylendopeptidase. The resulting peptides were purified by HPLC and then their sequences were determined by a peptide sequencer.2) Human serum MBP cDNA was cloned from human liver cDNA library, which had been carried in lambda gtll, by screening with rat serum MBP cDNA as a probe and the nucleotide sequence of the cloned cDNA was determined by … More dedeoxy termination method. By comparing the result obtained in 1) and 2), human serum MBP was revealed to be composed of 248 amino acids.3) The gross structure of the serum MBP is very similar to a complement component Clq. This prompted to us to study the molecular mechanism of complement activation by the serum MBP. Studies using the other complement components Clr and Cls revealed that the serum MBP, once bound to the solid phase ligands, associates Clr*Cls complement. On this complex, the conversion of Clr*Cls from their zymogen forms to the activated serine proteases proceeds, leading to the activating of a series of cascade reaction of the classical pathway of the complement system.4) The serum MBP was shown to have complement dependent bactericidal activity against E. coli K12, B strains which have haptenic sugars (mannose, NAcetylglucosamine) on their core structure, and also cytotoxic activity against cultured mammalian cells which have high mannose-type oligosaccharide chains on their surfaces. Less