Ikeda K, Sannoh T, Kawasaki N, Kawasaki T, Yamashina I
J Biol Chem. 1987 Jun 5;262(16):7451-4.
Serum mannan-binding protein (MBP), a lectin specific for mannose and N-acetylglucosamine, was revealed to activate the complement system as measured by passive hemolysis using sheep erythrocytes coated with yeast mannan. In contrast, rat liver MBP, which shares many properties in common with serum MBP, could not activate complement at all. The activation by serum MBP was inhibited effectively by the presence of haptenic sugars and dependent absolutely upon the presence of C4, indicating that the activation is initiated by the sugar binding activity of MBP and proceeds through the classical pathway. The 25 NH2-terminal amino acid sequence of rat serum MBP determined in this study was completely matched with that of MBP-A deduced from cDNA sequence by Drickamer et al. (Drickamer, K., Dordal, M. S., and Reynolds, L. (1986) J. Biol. Chem. 261, 6878-6887), revealing that MBP-A is in fact identical with serum MBP. On the basis of the knowledge of primary structures and physicochemical properties of rat serum and liver MBPs, a possible mechanism of the complement activation by serum MBP is discussed with reference to close similarity in the gross structures of serum MBP and C1q.
血清甘露聚糖结合蛋白（MBP）是一种对甘露糖和N - 乙酰葡糖胺具有特异性的凝集素，通过使用包被酵母甘露聚糖的绵羊红细胞进行被动溶血测定，发现它能激活补体系统。相比之下，与血清MBP具有许多共同特性的大鼠肝脏MBP根本不能激活补体。血清MBP的激活受到半抗原糖的有效抑制，并且绝对依赖于C4的存在，这表明激活是由MBP的糖结合活性启动，并通过经典途径进行。本研究中测定的大鼠血清MBP的25个NH2末端氨基酸序列与Drickamer等人从cDNA序列推导的MBP - A的序列完全匹配（Drickamer, K., Dordal, M. S., and Reynolds, L. (1986) J. Biol. Chem. 261, 6878 - 6887），表明MBP - A实际上与血清MBP相同。基于大鼠血清和肝脏MBP的一级结构和物理化学性质的知识，参考血清MBP和C1q总体结构的密切相似性，讨论了血清MBP激活补体的可能机制。
