Binding of cytosolic aconitase to the iron responsive element of porcine mitochondrial aconitase mRNA

Abstract The 5′ end of porcine mitochondrial aconitase mRNA contains an iron responsive element (IRE)-like secondary structure ( T. Dandekar, R. Stripecke, N. K. Gray, B. Goosen, A. Constable, H. E. Johansson, and M. W. Hentze (1991) EMBO J. 10, 1903–1909 ). A protein from a liver extract binds to a mitochondrial aconitase RNA probe and supports the identification of this sequence as an IRE. Purified cytosolic aconitase but not the mitochondrial enzyme binds to this IRE as well as to a ferritin IRE. All forms of cytosolic aconitase, [4Fe4S]enzyme, [3Fe4S] enzyme and apoenzyme bind with similar affinity. A K d of 0.25 n m was calculated for the apoaconitase-IRE interaction from Scatchard analysis. These results support the conclusion that cytosolic aconitase is an IRE-binding protein which may regulate translation of mitochondrial aconitase mRNA.