Kusche K, Burmester T
Institute of Zoology, University of Mainz, Müllerweg 6, Mainz, D-55099, Germany.
Biochem Biophys Res Commun. 2001 Apr 13;282(4):887-92. doi: 10.1006/bbrc.2001.4660.
In the American lobster, Homarus americanus, oxygen is transported by a hemocyanin that is composed 2 x 6 subunits. N-terminal sequencing show the presence of three distinct subunit types (alpha, beta and gamma). We cloned the cDNA of one of these subunits that belong to the alpha-type. It encodes a hemocyanin subunit of 654 amino acids with a molecular mass of 84.8 kDa, which is synthesized in the hepatopancreas. Phylogenetic analyses of the crustacean hemocyanin sequences show two well-separated clades, which correspond to the alpha and gamma-type subunits. Sequences of beta-type subunits are still unknown. The gamma-sequences have evolved about 15% faster than the alpha-subunits, consistent with the proposed conservative function of the latter. Under the assumption of a molecular clock we calculated that alpha- and gamma-subunits split about 214 +/- 14 million years ago, suggesting their divergence only in the decapod Crustacea.
在美洲龙虾（美洲螯龙虾）中，氧气由一种由2×6个亚基组成的血蓝蛋白运输。N端测序显示存在三种不同的亚基类型（α、β和γ）。我们克隆了其中一个属于α型的亚基的cDNA。它编码一个由654个氨基酸组成、分子量为84.8 kDa的血蓝蛋白亚基，该亚基在肝胰腺中合成。对甲壳类血蓝蛋白序列的系统发育分析显示有两个明显分开的进化枝，分别对应于α型和γ型亚基。β型亚基的序列仍然未知。γ型序列的进化速度比α型亚基快约15%，这与后者所提出的保守功能一致。在分子钟假设下，我们计算出α型和γ型亚基大约在2.14±0.14亿年前分开，这表明它们的分化仅发生在十足目甲壳动物中。
