Huang T S, Melefors O, Lind M I, Söderhäll K
Department of Physiological Mycology, University of Uppsala, Sweden.
Insect Biochem Mol Biol. 1999 Jan;29(1):1-9. doi: 10.1016/s0965-1748(98)00097-6.
A putative crayfish iron-responsive element (IRE) is present in the 5'-untranslated region of the crayfish ferritin mRNA. The putative crayfish IRE is in a cap-proximal position and shares most of the structural features of the consensus IRE, but the RNA stem-loop structure contains a bulge of a guanine instead of a cytosine at the expected position, so far thought to be a hallmark of IREs. By using an electromobility shift assay this IRE was shown to specifically bind purified recombinant human iron regulatory protein 1 (IRP1) as well as a factor(s) present in a homogenate of crayfish hepatopancreas, likely to be a crayfish IRP1 homologue. With mutations in the crayfish IRE, the affinity of IRP to IRE was drastically decreased. A cDNA encoding an IRP1-like protein was cloned from the hepatopancreas of crayfish. This protein has sequence similarities to IRP, and contains all the active-site residues of aconitase, two putative RNA-binding regions and a putative contact site between RNA and IRP. These results show that a crayfish IRE, lacking the bulged C, can bind IRP1 in vitro and that an IRP1-like protein present in crayfish hepatopancreas may have both aconitase and RNA-binding activities.
在小龙虾铁蛋白mRNA的5'-非翻译区存在一个假定的小龙虾铁反应元件（IRE）。这个假定的小龙虾IRE位于靠近帽子结构的位置，并且具有大多数共有IRE的结构特征，但是RNA茎环结构在预期位置含有一个鸟嘌呤凸起，而非胞嘧啶，而胞嘧啶凸起至今一直被认为是IRE的一个标志。通过电泳迁移率变动分析表明，这个IRE能特异性结合纯化的重组人铁调节蛋白1（IRP1）以及小龙虾肝胰腺匀浆中存在的一种因子，该因子可能是小龙虾IRP1的同源物。随着小龙虾IRE发生突变，IRP与IRE的亲和力急剧下降。从小龙虾的肝胰腺中克隆到一个编码类IRP1蛋白的cDNA。该蛋白与IRP具有序列相似性，并且含有乌头酸酶的所有活性位点残基、两个假定的RNA结合区域以及一个RNA与IRP之间的假定接触位点。这些结果表明，缺乏凸起胞嘧啶的小龙虾IRE在体外能结合IRP1，并且小龙虾肝胰腺中存在的类IRP1蛋白可能同时具有乌头酸酶和RNA结合活性。
