Philpott C C, 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.
Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):7321-5. doi: 10.1073/pnas.91.15.7321.
The iron-responsive element binding protein/cytosolic aconitase functions as either an RNA binding protein that regulates the uptake, sequestration, and utilization of iron or an enzyme that interconverts citrate and isocitrate. These mutually exclusive functions are regulated by changes in cellular iron levels. By site-directed mutagenesis we show that (i) ligation of a [4Fe-4S] cluster is necessary to inactivate RNA binding and activate enzyme function in vivo, (ii) three of four arginine residues of the aconitase active site participate in RNA binding, and (iii) aconitase activity is not required for iron-mediated regulation of RNA binding.
铁反应元件结合蛋白/胞质乌头酸酶既作为一种调节铁的摄取、螯合和利用的RNA结合蛋白，又作为一种催化柠檬酸和异柠檬酸相互转化的酶发挥作用。这些相互排斥的功能受细胞内铁水平变化的调节。通过定点诱变，我们发现：（i）[4Fe-4S]簇的连接对于在体内使RNA结合失活并激活酶功能是必需的；（ii）乌头酸酶活性位点的四个精氨酸残基中的三个参与RNA结合；（iii）铁介导的RNA结合调节不需要乌头酸酶活性。
