Butt J, Kim H Y, Basilion J P, Cohen S, Iwai K, Philpott C C, Altschul S, Klausner R D, Rouault T A
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 1996 Apr 30;93(9):4345-9. doi: 10.1073/pnas.93.9.4345.
Posttranscriptional regulation of genes of mammalian iron metabolism is mediated by the interaction of iron regulatory proteins (IRPs) with RNA stem-loop sequence elements known as iron-responsive elements (IREs). There are two identified IRPs, IRP1 and IRP2, each of which binds consensus IREs present in eukaryotic transcripts with equal affinity. Site-directed mutagenesis of IRP1 and IRP2 reveals that, although the binding affinities for consensus IREs are indistinguishable, the contributions of arginine residues in the active-site cleft to the binding affinity are different in the two RNA binding sites. Furthermore, although each IRP binds the consensus IRE with high affinity, each IRP also binds a unique alternative ligand, which was identified in an in vitro systematic evolution of ligands by exponential enrichment procedure. Differences in the two binding sites may be important in the function of the IRE-IRP regulatory system.
哺乳动物铁代谢基因的转录后调控是由铁调节蛋白（IRP）与称为铁反应元件（IRE）的RNA茎环序列元件相互作用介导的。已鉴定出两种IRP，即IRP1和IRP2，它们以相同的亲和力结合真核转录本中存在的共有IRE。对IRP1和IRP2进行定点诱变发现，尽管对共有IRE的结合亲和力难以区分，但活性位点裂隙中的精氨酸残基对两个RNA结合位点结合亲和力的贡献不同。此外，尽管每个IRP都以高亲和力结合共有IRE，但每个IRP也结合一种独特的替代配体，该配体是通过指数富集配体系统进化体外方法鉴定出来的。两个结合位点的差异可能对IRE-IRP调节系统的功能很重要。
