title: Genetic characterization and role in virulence of the ribonucleotide reductases of Streptococcus sanguinis.
abstract: Streptococcus sanguinis is a cause of infective endocarditis and has been shown to require a manganese transporter called SsaB for virulence and O2 tolerance. Like certain other pathogens, S. sanguinis possesses aerobic class Ib (NrdEF) and anaerobic class III (NrdDG) ribonucleotide reductases (RNRs) that perform the essential function of reducing ribonucleotides to deoxyribonucleotides. The accompanying paper (Makhlynets, O., Boal, A. K., Rhodes, D. V., Kitten, T., Rosenzweig, A. C., and Stubbe, J. (2014) J. Biol. Chem. 289, 6259-6272) indicates that in the presence of O2, the S. sanguinis class Ib RNR self-assembles an essential diferric-tyrosyl radical (Fe(III)2-Y(•)) in vitro, whereas assembly of a dimanganese-tyrosyl radical (Mn(III)2-Y(•)) cofactor requires NrdI, and Mn(III)2-Y(•) is more active than Fe(III)2-Y(•) with the endogenous reducing system of NrdH and thioredoxin reductase (TrxR1). In this study, we have shown that deletion of either nrdHEKF or nrdI completely abolishes virulence in an animal model of endocarditis, whereas nrdD mutation has no effect. The nrdHEKF, nrdI, and trxR1 mutants fail to grow aerobically, whereas anaerobic growth requires nrdD. The nrdJ gene encoding an O2-independent adenosylcobalamin-cofactored RNR was introduced into the nrdHEKF, nrdI, and trxR1 mutants. Growth of the nrdHEKF and nrdI mutants in the presence of O2 was partially restored. The combined results suggest that Mn(III)2-Y(•)-cofactored NrdF is required for growth under aerobic conditions and in animals. This could explain in part why manganese is necessary for virulence and O2 tolerance in many bacterial pathogens possessing a class Ib RNR and suggests NrdF and NrdI may serve as promising new antimicrobial targets.
authors.affiliation: From the Philips Institute for Oral Health Research, Virginia Commonwealth University, Richmond, Virginia 23298 and.
authors.forename: DeLacy V
authors.initials: DV
authors.lastname: Rhodes
authors.forename: Katie E
authors.initials: KE
authors.lastname: Crump
authors.forename: Olga
authors.initials: O
authors.lastname: Makhlynets
authors.forename: Melanie
authors.initials: M
authors.lastname: Snyder
authors.forename: Xiuchun
authors.initials: X
authors.lastname: Ge
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
authors.forename: JoAnne
authors.initials: J
authors.lastname: Stubbe
authors.forename: Todd
authors.initials: T
authors.lastname: Kitten
mesh_terms: D000332:Aerobiosis / Q000235:genetics; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D004697:Endocarditis, Bacterial / Q000201:enzymology / Q000235:genetics; D017353:Gene Deletion; D006801:Humans; D010100:Oxygen / Q000378:metabolism; D011817:Rabbits; D012264:Ribonucleotide Reductases / Q000235:genetics / Q000378:metabolism; D013290:Streptococcal Infections / Q000201:enzymology / Q000235:genetics; D013291:Streptococcus / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity; D037521:Virulence Factors
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors; C114872:NrdF protein, bacteria; D012264:Ribonucleotide Reductases; D010100:Oxygen
keywords: Bacterial Metabolism; Bacterial Pathogenesis; Infective Endocarditis; Manganese; Ribonucleotide Reductase; Streptococcus