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  • Title: High catalytic activity achieved with a mixed manganese-iron site in protein R2 of Chlamydia ribonucleotide reductase.
    Author: Voevodskaya N, Lendzian F, Ehrenberg A, Gräslund A.
    Journal: FEBS Lett; 2007 Jul 24; 581(18):3351-5. PubMed ID: 17601579.
    Abstract:
    Ribonucleotide reductase (class I) contains two components: protein R1 binds the substrate, and protein R2 normally has a diferric site and a tyrosyl free radical needed for catalysis. In Chlamydia trachomatis RNR, protein R2 functions without radical. Enzyme activity studies show that in addition to a diiron cluster, a mixed manganese-iron cluster provides the oxidation equivalent needed to initiate catalysis. An EPR signal was observed from an antiferromagnetically coupled high-spin Mn(III)-Fe(III) cluster in a catalytic reaction mixture with added inhibitor hydroxyurea. The manganese-iron cluster in protein R2 confers much higher specific activity than the diiron cluster does to the enzyme.
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