Evolution of molluscan hemocyanins as deduced from DNA sequencing.
Evolution of molluscan hemocyanins as deduced from DNA sequencing.
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根据 DNA 测序推断软体动物血蓝蛋白的进化。
DOI：
10.1016/j.micron.2003.10.035
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发表时间：
2004
期刊：
影响因子：
2.4
通讯作者：
J. Markl
中科院分区：
文献类型：
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作者：
B. Lieb;J. Markl
软体动物血蓝蛋白是由350-400 kDa的多肽亚基组成的巨大圆柱形组装体，该亚基被细分为7或8个共价连接的功能单元（FU，称为a至h）。50 kDa（详情参见Meissner等人，2000）。每个FU能够可逆地结合双氧分子。这项研究是基于13个血蓝蛋白（其术语，见图1）的序列信息，从四个不同的动物纲的软体动物。我们使用相邻连接方法、最大简约法和贝叶斯推断从多个序列比对计算系统发育树（Felsenstein，1988; Kumar等人，2001; Whelan and Goldman，2001）.所有这些树导致了各个功能单元的可比较拓扑结构;图1中显示了一个示例。如通过成对比较HtH 1和OdH已经观察到的（Lieb等人，2000），拓扑上对应的FU也被一起分组在该加宽的遗传树的相同分支中。这进一步证实了我们先前的假设，即编码血蓝蛋白的基因从原始的单个FU基因进化而来（通过三个随后的基因复制和融合），并且这发生在软体动物门分裂成现存的类别之前。由于一个足够的外群仍然缺乏，树仍然unrooted.Several研究的软体动物表现出两个相当不同的血蓝蛋白亚型，这几乎可以肯定起源于一个单一的八FU基因的复制。从图1中的树中可以很清楚地看到，这些重复事件独立地发生了几次，因为一方面是NnH 1/NnH 2，另一方面是HtH 1/HtH 2/KLH 1/KLH 2，它们是两个不同分支的成员，这些分支是高度自举支持的。第三个分支由RtH 2 e形成，表明产生同种型对RtH 1/RtH 2的重复也是独立发生的（Gebauer等人，1999年）。此外，从
Molluscan hemocyanins are huge cylindrical assemblies constructed from a 350–400 kDa polypeptide, the subunit, which is subdivided into 7 or 8 covalently-linked functional units (FUs, termed a to h) of ca. 50 kDa (for details, see Meissner et al., 2000). Each FU is able to reversibly bind a dioxygen molecule. This study is based on the sequence information of 13 hemocyanins (for their terminology, see Fig. 1) from four different animal classes of the phylum Mollusca. We calculated phylogenetic trees from multiple sequence alignments, using neighbour joining methods, maximum parsimony and the Baysian inference (Felsenstein, 1988; Kumar et al., 2001; Whelan and Goldman, 2001). All these trees resulted in a comparable topology of the individual functional units; an example is shown in Fig. 1. As already been observed by comparing HtH1 and OdH pairwise (Lieb et al., 2000), topologically corresponding FUs are also grouped together in the same branch of this broadened phylogenic tree. This further substantiates our earlier hypothesis that the gene encoding hemocyanin evolved from a primordial single FU gene (by three subsequent gene duplications and fusions), and that this occurred well before the phylum Mollusca split into its extant classes. Since an adequate outgroup is still lacking, the tree remains unrooted.Several of the molluscs studied exhibit two rather different hemocyanin isoforms, which almost certainly originated from duplication of a single eight-FU-gene. From the tree in Fig. 1 it is very clear that these duplication events occurred several times independently, because NnH1/NnH2 on the one hand and HtH1/HtH2/KLH1/KLH2 on the other are members of two different branches which are highly bootstrap-supported. A third branch is formed by RtH2e, indicating that also the duplication yielding the isoform pair RtH1/RtH2 occurred independently (Gebauer et al., 1999). Moreover, it is clear from