Structure and function of mannan-binding proteins isolated from human liver and serum.
Structure and function of mannan-binding proteins isolated from human liver and serum.
复制标题
从人肝脏和血清中分离的甘露聚糖结合蛋白的结构和功能。
DOI：
10.1093/oxfordjournals.jbchem.a124471
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发表时间：
1994
影响因子：
2.7
通讯作者：
Toshisuke Kawasaki
中科院分区：
文献类型：
--
作者：
Hiroshi Kurata;T. Sannoh;Y. Kozutsumi;Yasunori Yokota;Toshisuke Kawasaki
甘露聚糖结合蛋白（MBPs）有两种形式，都是在肝脏中合成的。虽然已经克隆了大鼠和小鼠的两种不同的MBP cDNA，但只分离出一种形式的人MBP cDNA。在这项研究中，两种形式的人MBP，肝MBP（L-MBP）和血清MBP（S-MBP），从肝脏和血清中纯化和表征，分别。这两个人MBP的氨基酸序列是相同的，并与从cDNA序列推断的那些一致。L-MBP和S-MBP的最大差异是亚基数目，L-MBP约为9个，S-MBP约为18个。此外，S-MBP具有激活补体的能力，而L-MBP没有。这些结果表明，一种新合成的蛋白质在人肝脏中经过后处理，形成两种形式，S-MBP和L-MBP。在COS-1细胞中合成的重组MBP，转染人MBP cDNA后，分泌到培养基中，表明COS-1细胞缺乏分化S-MBP和L-MBP的机制。在COS-1细胞中合成的突变MBP缺乏在胶原样结构域的起始处包含9个氨基酸残基的序列，该突变MBP没有激活补体的能力，这表明该序列在人MBP激活补体中起重要作用。
Mannan-binding proteins (MBPs) occur in two forms, both of which are synthesized in the liver. Although two different MBP cDNAs have been cloned and characterized for rat and mouse, only one form of human MBP cDNA has been isolated. In this study, two forms of human MBP, liver MBP (L-MBP) and serum MBP (S-MBP), were purified from liver and serum and characterized, respectively. The amino acid sequences of these two human MBPs were identical and consistent with those deduced from the cDNA sequence. The most significant difference between L-MBP and S-MBP was the number of subunits, which was about 9 in L-MBP and 18 in S-MBP. Furthermore, S-MBP but not L-MBP had the ability to activate the complement. These results suggested that a newly synthesized protein is processed post-translationally into two forms, S-MBP and L-MBP, in human liver. Recombinant MBP synthesized in COS-1 cells, after transfection with human MBP cDNA, was secreted into the medium, suggesting that COS-1 cells lack a mechanism for differentiating S-MBP and L-MBP. A mutant MBP synthesized in COS-1 cells which lacked a sequence comprising 9 amino acid residues at the beginning of the collagen-like domain had no ability to activate the complement, suggesting that this sequence plays an important role in the activation of the complement by human MBP.