title: A Mycobacterium tuberculosis ligand-binding Mn/Fe protein reveals a new cofactor in a remodeled R2-protein scaffold.
abstract: Chlamydia trachomatis R2c is the prototype for a recently discovered group of ribonucleotide reductase R2 proteins that use a heterodinuclear Mn/Fe redox cofactor for radical generation and storage. Here, we show that the Mycobacterium tuberculosis protein Rv0233, an R2 homologue and a potential virulence factor, contains the heterodinuclear manganese/iron-carboxylate cofactor but displays a drastic remodeling of the R2 protein scaffold into a ligand-binding oxidase. The first structural characterization of the heterodinuclear cofactor shows that the site is highly specific for manganese and iron in their respective positions despite a symmetric arrangement of coordinating residues. In this protein scaffold, the Mn/Fe cofactor supports potent 2-electron oxidations as revealed by an unprecedented tyrosine-valine crosslink in the active site. This wolf in sheep's clothing defines a distinct functional group among R2 homologues and may represent a structural and functional counterpart of the evolutionary ancestor of R2s and bacterial multicomponent monooxygenases.
authors.affiliation: Stockholm Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences C4, SE-106 91 Stockholm, Sweden.
authors.forename: Charlotta S
authors.initials: CS
authors.lastname: Andersson
authors.forename: Martin
authors.initials: M
authors.lastname: Högbom