Heterogeneity and differential expression under hypoxia of two-domain hemoglobin chains in the water flea, Daphnia magna
Heterogeneity and differential expression under hypoxia of two-domain hemoglobin chains in the water flea, Daphnia magna
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DOI：
10.1074/jbc.274.15.10649
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发表时间：
1999-04-09
影响因子：
4.8
通讯作者：
Yamagata, H
中科院分区：
文献类型：
--
作者：
Kimura, S;Tokishita, S;Yamagata, H
用双向凝胶电泳技术分析了低氧条件下饲养的大型蚤（Daphnia magna）的血红蛋白（Hb）。血红蛋白由6个主要亚基链组成（命名为DHbA至DHbF）。DHbA、DHbB、DHbC和DHbF的NH 2端氨基酸序列彼此不同，表明D. magna. DHbD和DHbE的NH 2-末端氨基酸序列分别与DHbA和DHbB的相同。六个血红蛋白链也被发现在正常氧下饲养的动物在少量和改变的组合物;在正常氧下的减少的程度较高的DHbC，DHbD，和DHbF的量比其他人。这些结果表明Hb基因受环境氧浓度的差异调节。在D. dhb 1、dhb 2和dhb 3基因的全序列和cDNA序列分析表明，dhb 1、dhb 2和dhb 3基因具有7个外显子、6个内含子的结构。该结构由一个内含子分隔编码分泌信号序列的外显子，两个大的重复区域的三个外显子，两个内含子结构，编码每个域含有血红素结合位点，和一个内含子桥接两个重复区域。推导的氨基酸序列同源性均在79%以上，具有D.大血红蛋白链。分析还表明，DHbB（或DHbE），DHbF和DHbC分别由dhb 1，dhb 2和dhb 3基因编码。
Hemoglobin (Hb) purified from the water flea, Daphnia magna, reared under hypoxia was analyzed by two dimensional gel electrophoresis. The Hb was shown to be composed of six major subunit chain species (designated as DHbA to DHbF). The NH2-terminal amino acid sequences of DHbA, DHbB, DHbC, and DHbF are different from one another, indicating that at least four Hb genes are present in D. magna. The NH2-terminal amino acid sequences of DHbD and DHbE are the same as those of DHbA and DHbB, respectively. The six Hb chains were also found in the animal reared under normoxia in small amounts and with altered composition; the extent of decrease under normoxia was higher in the amounts of DHbC, DHbD, and DHbF than those of others. These results indicate that the Hb genes are differentially regulated by the ambient oxygen concentration. Four Hb genes constituting a cluster in the order, dhb4, dhb3, dhb1, and dhb2, were found on the chromosome of D. magna, The complete nucleotide sequences of the dhb1, dhb2, and dhb3 genes and their cDNAs showed that the genes have a seven-exon, six-intron structure. The structure consists of an intron separating an exon encoding a secretory signal sequence, two large repeated regions of a three-exon, two-intron structure that encode each a domain containing a heme-binding site, and an intron bridging the two repeated regions. The deduced amino acid sequences of the gene products showed higher than 79% identity to one another and showed unique features conserved in D. magna Hb chains. The analysis also suggested that DHbB (or DHbE), DHbF, and DHbC are encoded by the dhb1, dhb2, and dhb3 genes, respectively.