Pont-Kingdon G A, Beagley C T, Okimoto R, Wolstenholme D R
Department of Biology, University of Utah, Salt Lake City 84112.
J Mol Evol. 1994 Oct;39(4):387-99. doi: 10.1007/BF00160271.
The nucleotide sequence of a segment of the mitochondrial DNA (mtDNA) molecule of the sea anemone Metridium senile (phylum Cnidaria, class Anthozoa, order Actiniaria) has been determined, within which have been identified the genes for respiratory chain NADH dehydrogenase subunit 2 (ND2), the small-subunit rRNA (s-rRNA), cytochrome c oxidase subunit II (COII), ND4, ND6, cytochrome b (Cyt b), tRNA(f-Met), and the large-subunit rRNA (1-rRNA). The eight genes are arranged in the order given and are all transcribed from the same strand of the molecule. The overall order of the M. senile mt-genes differs from that of other metazoan mtDNAs. In M. senile mt-protein genes, AGA and AGG codons appear to have the standard genetic code specification of arginine, rather than serine as found for other invertebrate mt-genetic codes. Also, ATA has the standard genetic code specification of isoleucine. TGA occurs in three M. senile mt-protein genes and may specify tryptophan as in other metazoan, protozoan, and some fungal mt-genetic codes. The M. senile mt-rRNA(f-Met) gene has primary and secondary structure features closely resembling those of the Escherichia coli initiator tRNA, including standard dihydrouridine and T psi C loop sequences and a mismatch pair at the top of the aminoacyl stem. Determinations of the 5' and 3' end nucleotides of the M. senile mt-s-rRNAs indicated that these molecules have a homogenous size of 1,081 ntp, larger than any other known metazoan mt-s-rRNAs. Consistent with its larger size, the M. senile mt-s-rRNA can be folded into a secondary structure that more closely resembles that of the E. coli 16S rRNA than can any other metazoan mt-s-rRNA. These findings concerning M. senile mtDNA indicate that most of the unusual features regarding metazoan mt-genetic codes, rRNAs, and probably tRNAs developed after divergence of the Cnidarian line from the ancestral line common to other metazoa.
已确定了海葵（分类地位：刺胞动物门、珊瑚纲、海葵目）老年大海葵线粒体DNA（mtDNA）分子一段的核苷酸序列，其中已鉴定出呼吸链NADH脱氢酶亚基2（ND2）、小亚基rRNA（s-rRNA）、细胞色素c氧化酶亚基II（COII）、ND4、ND6、细胞色素b（Cyt b）、tRNA（f-Met）和大亚基rRNA（1-rRNA）的基因。这八个基因按给定顺序排列，且都从分子的同一条链转录。老年大海葵线粒体基因的总体顺序不同于其他后生动物的线粒体DNA。在老年大海葵线粒体蛋白质基因中，AGA和AGG密码子似乎具有精氨酸的标准遗传密码指定，而不像其他无脊椎动物线粒体遗传密码那样指定丝氨酸。此外，ATA具有异亮氨酸的标准遗传密码指定。TGA出现在三个老年大海葵线粒体蛋白质基因中，可能像其他后生动物、原生动物和一些真菌线粒体遗传密码那样指定色氨酸。老年大海葵线粒体rRNA（f-Met）基因具有与大肠杆菌起始tRNA非常相似的一级和二级结构特征，包括标准的二氢尿嘧啶和TψC环序列以及氨酰基茎顶部的错配碱基对。对老年大海葵线粒体s-rRNA的5'和3'末端核苷酸的测定表明，这些分子的大小均一，为1081个核苷酸，比任何其他已知的后生动物线粒体s-rRNA都大。与其较大的尺寸一致，老年大海葵线粒体s-rRNA可以折叠成一种二级结构，这种结构比任何其他后生动物线粒体s-rRNA更类似于大肠杆菌16S rRNA。这些关于老年大海葵线粒体DNA的发现表明，后生动物线粒体遗传密码、rRNA以及可能的tRNA的大多数异常特征是在刺胞动物谱系从其他后生动物共有的祖先谱系分化之后出现的。
