Department of Marine Biology, Ocean University of China, 266003, Qingdao, People's Republic of China.
Mol Biol Rep. 2010 Jun;37(5):2279-83. doi: 10.1007/s11033-009-9720-2. Epub 2009 Aug 15.
Promethins have been shown to be present in the vertebrates examined so far, yet little is known to date about them in invertebrates. Here we isolated a cDNA encoding a promethin-like homolog from the gut cDNA library of the amphioxus Branchiostoma belcheri, a cephalochordate occupying a nodal position transient from invertebrates to vertebrates. It contained a 504 bp open reading frame corresponding to a protein of 167 amino acids. Primary structural examination showed that the deduced promethin-like homolog was a transmembrane protein with three potential transmembrane helices, resembling the vertebrate promethins. Phylogenetic analysis showed that B. belcheri promethin-like homolog was located at the base of the vertebrate counterparts, suggesting that it represents the archetype of vertebrate promethins. Both Northern blotting and in situ hybridization histochemistry revealed a tissue-specific expression pattern of promethin-like gene, like that of mammalian promethins. This is the first report on invertebrate promethin-like homolog, paving the way for further insights into the evolution and function of promethins.
迄今为止，已经在研究的脊椎动物中发现了 Promethin 的存在，但目前对无脊椎动物中的 Promethin 知之甚少。在这里，我们从文昌鱼（Branchiostoma belcheri）的肠道 cDNA 文库中分离出了一个编码 Promethin 样同系物的 cDNA，文昌鱼是一种处于从无脊椎动物到脊椎动物的过渡节点的头索动物。它包含一个 504bp 的开放阅读框，对应一个 167 个氨基酸的蛋白质。初步结构分析表明，推断的 Promethin 样同系物是一种具有三个潜在跨膜螺旋的跨膜蛋白，类似于脊椎动物的 Promethin。系统发育分析表明，文昌鱼 Promethin 样同系物位于脊椎动物对应物的基部，表明它代表了脊椎动物 Promethin 的原型。Northern blot 和原位杂交组织化学都揭示了 Promethin 样基因的组织特异性表达模式，类似于哺乳动物 Promethin。这是首次报道无脊椎动物 Promethin 样同系物，为进一步深入了解 Promethin 的进化和功能铺平了道路。
