Coelomocytes express SpBf, a homologue of factor B, the second component in the sea urchin complement system.
Coelomocytes express SpBf, a homologue of factor B, the second component in the sea urchin complement system.
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DOI：
10.4049/jimmunol.161.12.6784
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发表时间：
1998-12
影响因子：
4.4
通讯作者：
L. Smith;C. Shih;Sebastian G. Dachenhausen
中科院分区：
文献类型：
--
作者：
L. Smith;C. Shih;Sebastian G. Dachenhausen
从紫海胆（Strongylocentrotus purpuratus）的LPS激活的体腔细胞cDNA文库中克隆了因子B的同源物SpBf并进行了序列测定。推导的氨基酸序列和结构域结构与脊椎动物Bf/C2家族蛋白具有显著的相似性。SpBf是一种嵌合蛋白，由五个短的共有重复序列、一个血管性血友病因子结构域和一个丝氨酸蛋白酶结构域组成。它的推导分子量为91 kDa，具有推定的因子D蛋白酶的保守切割位点。它有10个N-连接糖基化的共有识别位点。脊椎动物C2/Bf蛋白中参与Mg 2+结合和丝氨酸蛋白酶活性的氨基酸在SpBf中是保守的。系统发育分析表明，SpBf是脊椎动物Bf/C2家族中最古老的成员。另外的SCR系统发育分析表明，SpBf中的5个SCR可能是3个SCR的祖先，这是脊椎动物Bf/C2蛋白中的典型模式。RNA凝胶印迹显示SpBf转录物为5.5 kb，并且在体腔细胞中特异性表达。基因组杂交结果表明，SpBf基因（Sp152）是单拷贝基因每个单倍体基因组。这是从海胆中鉴定的第二种补体成分，并且与海胆C3同源物一起，这两种成分可能是与高等脊椎动物中的替代途径同源的简单补体系统的一部分。
A homologue of factor B, SpBf, has been cloned and sequenced from an LPS-activated coelomocyte cDNA library from the purple sea urchin, Strongylocentrotus purpuratus. The deduced amino acid sequence and domain structure show significant similarity to the vertebrate Bf/C2 family proteins. SpBf is a mosaic protein, composed of five short consensus repeats, a von Willebrand Factor domain, and a serine protease domain. It has a deduced molecular mass of 91 kDa, with a conserved cleavage site for a putative factor D protease. It has ten consensus recognition sites for N-linked glycosylation. Amino acids involved in both Mg2+ binding and in serine protease activity in the vertebrate C2/Bf proteins are conserved in SpBf. Phylogenetic analysis of SpBf indicates that it is the most ancient member of the vertebrate Bf/C2 family. Additional phylogenetic analysis of the SCRs indicates that five SCRs in SpBf may be ancestral to three SCRs, which is the typical pattern in the vertebrate Bf/C2 proteins. RNA gel blots show that SpBf transcripts are 5.5 kb and are specifically expressed in coelomocytes. Genome blots suggest that the SpBf gene (Sp152) is single copy gene per haploid genome. This is the second complement component to be identified from the sea urchin, and, with the sea urchin C3 homologue, these two components may be part of a simple complement system that is homologous to the alternative pathway in higher vertebrates.