Castresana J, Feldmaier-Fuchs G, Yokobori S, Satoh N, Pääbo S
Institute of Zoology, University of Munich, D-80333 Munich, Germany.
Genetics. 1998 Nov;150(3):1115-23. doi: 10.1093/genetics/150.3.1115.
The complete nucleotide sequence of the mitochondrial genome of the hemichordate Balanoglossus carnosus (acorn worm) was determined. The arrangement of the genes encoding 13 protein, 22 tRNA, and 2 rRNA genes is essentially the same as in vertebrates, indicating that the vertebrate and hemichordate mitochondrial gene arrangement is close to that of their common ancestor, and, thus, that it has been conserved for more than 600 million years, whereas that of echinoderms has been rearranged extensively. The genetic code of hemichordate mitochondria is similar to that of echinoderms in that ATA encodes isoleucine and AGA serine, whereas the codons AAA and AGG, whose amino acid assignments also differ between echinoderms and vertebrates, are absent from the B. carnosus mitochondrial genome. There are three noncoding regions of length 277, 41, and 32 bp: the larger one is likely to be equivalent to the control region of other deuterostomes, while the two others may contain transcriptional promoters for genes encoded on the minor coding strand. Phylogenetic trees estimated from the inferred protein sequences indicate that hemichordates are a sister group of echinoderms.
已确定半索动物肉球肠鳃纲动物（柱头虫）线粒体基因组的完整核苷酸序列。编码13种蛋白质、22种tRNA和2种rRNA基因的排列方式与脊椎动物基本相同，这表明脊椎动物和半索动物的线粒体基因排列方式与其共同祖先的排列方式相近，因此这种排列方式已经保守了超过6亿年，而棘皮动物的排列方式则发生了广泛重排。半索动物线粒体的遗传密码与棘皮动物的相似，即ATA编码异亮氨酸，AGA编码丝氨酸，而在肉球肠鳃纲动物线粒体基因组中不存在AAA和AGG密码子，这两个密码子在棘皮动物和脊椎动物中的氨基酸分配也有所不同。有三个长度分别为277、41和32 bp的非编码区：较大的一个可能相当于其他后口动物的控制区，而另外两个可能包含小编码链上编码基因的转录启动子。根据推断的蛋白质序列估计的系统发育树表明，半索动物是棘皮动物的姐妹群。
