Download MendeleyA Structurally Divergent Class Ia Ribonucleotide Reductase from a Tick-Borne Pathogen.
Peduzzi, O.M., Palowitch, G.M., Gajewski, J.P., Hu, K., Wheeler, A., Laremore, T.N., Silletti, S., Komives, E.A., Allen, B.D., Silakov, A., Krebs, C., Bollinger Jr., J.M., Lin, C.Y., Boal, A.K.(2025) Biochemistry 64: 3935-3955
- PubMed: 40877217
- DOI: https://doi.org/10.1021/acs.biochem.5c00316
- Primary Citation of Related Structures:
9DWS - PubMed Abstract:
Ribonucleotide reductases (RNRs) generate 2'-deoxynucleotides for DNA biosynthesis, a reaction essential to all life. Class I RNRs have two subunits, α and β. α binds and reduces the substrate, whereas β oxidizes one of the cysteines in α to a C3'-H-bond-cleaving thiyl radical to begin the reaction. The α-Cys oxidant in β is variously a tyrosyl radical (Y • ) generated by a diiron or dimanganese cluster, a high-valent dimetal cluster [Mn(IV)/Fe(III) or Mn 2 (IV/III)], or a dihydroxylphenylalanine (DOPA) radical that operates without need of a transition metal. The metal (in)dependence of the Cys oxidant in β correlates loosely with sequence-similarity groupings. We show here that Francisella hispaniensis ( Fh ) β, which lies within an uncharacterized sequence cluster that contains orthologs from multiple human pathogens, harbors a Fe 2 (III/III)/Y • cofactor, as in class Ia RNRs from eukaryotes and Escherichia coli . Fh β has several unusual structural features that may reflect adaptation to the bacterium's environment(s). In its apo form, an unwound helix everts a metal ligand toward solvent, and the radical-harboring Y points away from the diiron cluster. An additional aromatic residue (W194), conserved within the sequence cluster, is found close to the universally conserved W37, which is thought to mediate α-Cys oxidation in all class I enzymes. The Y • in resting β is remarkably resistant to reduction by hydroxyurea but becomes 8000 times more sensitive when β is engaged in turnover with α. These structural and functional distinctions could be counter measures against host redox defenses that would target the pathogen's RNR and its cofactor.
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Organizational Affiliation:
