Class Id ribonucleotide reductase utilizes a Mn2(IV,III) cofactor and undergoes large conformational changes on metal loading

• DOI: 10.1007/s00775-019-01697-8
• Publication Date: 2019-08-14T23:03:00Z
• Authors: Inna Rozman Grinberg; Sigrid Berglund; Mahmudul Hasan; Daniel Lundin; Felix M. Ho; Ann Magnuson; Derek T. Logan; Britt-Marie Sjöberg; Gustav Berggren
• Keywords: Ribonucleotide reductase; Ribonucleotide

Outside of the photosynthetic machinery, high-valent manganese cofactors are rare in biology. It was proposed that a recently discovered subclass ribonucleotide reductase (RNR), class Id, is dependent on Mn2(IV,III) cofactor for catalysis. Class I RNRs consist substrate-binding component (NrdA) and metal-containing radical-generating (NrdB). Herein we utilize combination EPR spectroscopy enzyme assays to underscore enzymatic relevance Id NrdB from Facklamia ignava. Once formed, confers activity correlates well with quantity. Moreover, present X-ray structure apo- aerobically Mn-loaded forms homologous Leeuwenhoekiella blandensis, revealing dimanganese centre typical subclass, tyrosine residue maintained at distance metal lysine projected towards metals. Structural comparison metal-loaded protein reveals refolding loop containing conserved an unusual shift orientation helices within monomer, leading opening channel site. Such major conformational changes have not been observed proteins before. Finally, vitro reconstitution experiments reveal formed spontaneously oxygen, but can be generated least two different reduced oxygen species, i.e. H2O2 superoxide (O 2 ·− ). Considering differences efficiency these activating reagents, propose physiologically relevant mechanism involves superoxide.