Papanastasiou Anastasios D, Zarkadis Ioannis K
Department of Biology, School of Medicine, University of Patras, Rion 26500 Patra, Greece.
Dev Comp Immunol. 2006;30(5):485-91. doi: 10.1016/j.dci.2005.06.023. Epub 2005 Aug 1.
Of the 35 proteins, enzymes, receptors and regulatory components of the complement system, C8gamma is unique in that it is the only lipocalin. C8gamma is a subunit of the C8 molecule, which is one of the five components (C5b, C6, C7, C8 and C9) that interact as a consequence of complement activation to form the membrane attack complex. Until now, C8gamma has been characterized only in mammalian species. In order to elucidate the phylogeny of this molecule, we have cloned the C8gamma subunit in rainbow trout (Oncorhynchus mykiss), a teleost fish representing a critical point in the evolutionary divergence of the complement system. The deduced amino acid sequence of trout C8gamma shows significant identity (37%) to the human C8gamma homolog and much lower to the other known lipocalins. The lipocalin domain is present and all the cysteine residues are conserved. The trout C8gamma gene is probably present as a single copy in the trout genome showing a differential expression pattern among tissues investigated.
在补体系统的35种蛋白质、酶、受体和调节成分中，C8γ独一无二，因为它是唯一的脂质运载蛋白。C8γ是C8分子的一个亚基，C8分子是补体激活后相互作用形成膜攻击复合物的五个成分（C5b、C6、C7、C8和C9）之一。到目前为止，C8γ仅在哺乳动物物种中得到表征。为了阐明该分子的系统发育，我们在虹鳟鱼（Oncorhynchus mykiss）中克隆了C8γ亚基，虹鳟鱼是一种硬骨鱼，代表了补体系统进化分歧中的一个关键点。虹鳟鱼C8γ的推导氨基酸序列与人类C8γ同源物具有显著的同一性（37%），与其他已知的脂质运载蛋白的同一性则低得多。脂质运载蛋白结构域存在，所有半胱氨酸残基均保守。虹鳟鱼C8γ基因可能在虹鳟鱼基因组中以单拷贝形式存在，在所研究的组织中表现出差异表达模式。
