CMP-N-ACETYLNEURAMINIC ACID HYDROXYLASE - THE FIRST CYTOSOLIC RIESKE IRON-SULFUR PROTEIN TO BE DESCRIBED IN EUKARYA

Electron paramagnetic resonance (EPR) spectroscopy and analysis of the primary structure of the CMP-N-acetylneuraminic acid hydroxylase reve aled that this enzyme is the first iron-sulphur protein of the Rieske type to be found in the cytosol of Eukarya, The dithionite-reduced hyd roxylase exhibited an EPR signal known to be characteristic for a Ries ke iron-sulphur centre (2Fe-2S), the g-values being 1.78, 1.91 and 2.0 1, respectively, An analysis of the primary structure of the hydroxyla se led to the identification of an amino acid sequence, known to be ch aracteristic for Rieske proteins, Furthermore, possible binding sites for cytochrome b(5), the substrate CMP-Neu5Ac and a mononuclear iron c entre were also identified.