4D8F

Chlamydia trachomatis NrdB with a Mn/Fe cofactor (procedure 1 - high Mn)

Summary for 4D8F

• Entry DOI: 10.2210/pdb4d8f/pdb
• Related: 4D8G
• Descriptor: Ribonucleoside-diphosphate reductase subunit beta, FE (III) ION, MANGANESE (II) ION, ... (5 entities in total)
• Functional Keywords: iron, manganese, ribonucleotide reductase, metalloenzyme, oxidoreductase
• Biological source: Chlamydia trachomatis
• Total number of polymer chains: 4
• Total formula weight: 171622.01

Authors

Dassama, L.M.K.,Boal, A.K.,Krebs, C.,Rosenzweig, A.C.,Bollinger Jr., J.M. (deposition date: 2012-01-10, release date: 2012-02-15, Last modification date: 2023-09-13)

Primary citation

Dassama, L.M.,Boal, A.K.,Krebs, C.,Rosenzweig, A.C.,Bollinger, J.M.
Evidence that the beta subunit of Chlamydia trachomatis ribonucleotide reductase is active with the manganese ion of its manganese(IV)/iron(III) cofactor in site 1.
J.Am.Chem.Soc., 134:2520-2523, 2012

PubMed Abstract: The reaction of a class I ribonucleotide reductase (RNR) begins when a cofactor in the β subunit oxidizes a cysteine residue ~35 Å away in the α subunit, generating a thiyl radical. In the class Ic enzyme from Chlamydia trachomatis (Ct), the cysteine oxidant is the Mn(IV) ion of a Mn(IV)/Fe(III) cluster, which assembles in a reaction between O(2) and the Mn(II)/Fe(II) complex of β. The heterodinuclear nature of the cofactor raises the question of which site, 1 or 2, contains the Mn(IV) ion. Because site 1 is closer to the conserved location of the cysteine-oxidizing tyrosyl radical of class Ia and Ib RNRs, we suggested that the Mn(IV) ion most likely resides in this site (i.e., (1)Mn(IV)/(2)Fe(III)), but a subsequent computational study favored its occupation of site 2 ((1)Fe(III)/(2)Mn(IV)). In this work, we have sought to resolve the location of the Mn(IV) ion in Ct RNR-β by correlating X-ray crystallographic anomalous scattering intensities with catalytic activity for samples of the protein reconstituted in vitro by two different procedures. In samples containing primarily Mn(IV)/Fe(III) clusters, Mn preferentially occupies site 1, but some anomalous scattering from site 2 is observed, implying that both (1)Mn(II)/(2)Fe(II) and (1)Fe(II)/(2)Mn(II) complexes are competent to react with O(2) to produce the corresponding oxidized states. However, with diminished Mn(II) loading in the reconstitution, there is no evidence for Mn occupancy of site 2, and the greater activity of these "low-Mn" samples on a per-Mn basis implies that the (1)Mn(IV)/(2)Fe(III)-β is at least the more active of the two oxidized forms and may be the only active form.

PubMed: 22242660
DOI: 10.1021/ja211314p

Experimental method

X-RAY DIFFRACTION (2.2 Å)