Aconitase, a two-faced protein: enzyme and iron regulatory factor.

In this brief survey, the path of development of our knowledge of the iron-sulfur enzyme aconitase [citrate(isocitrate)hydrolyase EC4.2.1.3.] is traced from its discovery in 1937. Particular emphasis is on developments in the past decade, when EPR, Mossbauer and electron nuclear double resonance spectroscopies, X-ray crystallography, and mutational analysis were applied to the problem. More recently discovered was the significant amino acid sequence identity between mitochondrial aconitase and the iron regulatory factor or iron-responsive element binding protein (IRE-BP). This has led to the realization that IRE-BP is an alternative form of cytosolic (not of mitochondrial) aconitase that is devoid of its cubane Fe-S cluster.