scholarly journals Mechanism of Assembly of the Dimanganese-Tyrosyl Radical Cofactor of Class Ib Ribonucleotide Reductase: Enzymatic Generation of Superoxide Is Required for Tyrosine Oxidation via a Mn(III)Mn(IV) Intermediate

2013 ◽  
Vol 135 (10) ◽  
pp. 4027-4039 ◽  
Author(s):  
Joseph A. Cotruvo ◽  
Troy A. Stich ◽  
R. David Britt ◽  
JoAnne Stubbe
Keyword(s):  
Ribonucleotide Reductase ◽  
Tyrosyl Radical ◽  
Tyrosine Oxidation ◽  
Class Ib

scholarly journals NrdI Essentiality for Class Ib Ribonucleotide Reduction in Streptococcus pyogenes

2008 ◽  
Vol 190 (14) ◽  
pp. 4849-4858 ◽  
Author(s):  
Ignasi Roca ◽  
Eduard Torrents ◽  
Margareta Sahlin ◽  
Isidre Gibert ◽  
Britt-Marie Sjöberg
Keyword(s):  
Streptococcus Pyogenes ◽  
Ribonucleotide Reductase ◽  
Tyrosyl Radical ◽  
Iron Site ◽  
Direct Role ◽  
Dinuclear Iron ◽  
Class Ib

ABSTRACT The Streptococcus pyogenes genome harbors two clusters of class Ib ribonucleotide reductase genes, nrdHEF and nrdF*I*E*, and a second stand-alone nrdI gene, designated nrdI2. We show that both clusters are expressed simultaneously as two independent operons. The NrdEF enzyme is functionally active in vitro, while the NrdE*F* enzyme is not. The NrdF* protein lacks three of the six highly conserved iron-liganding side chains and cannot form a dinuclear iron site or a tyrosyl radical. In vivo, on the other hand, both operons are functional in heterologous complementation in Escherichia coli. The nrdF*I*E* operon requires the presence of the nrdI* gene, and the nrdHEF operon gained activity upon cotranscription of the heterologous nrdI gene from Streptococcus pneumoniae, while neither nrdI* nor nrdI2 from S. pyogenes rendered it active. Our results highlight the essential role of the flavodoxin NrdI protein in vivo, and we suggest that it is needed to reduce met-NrdF, thereby enabling the spontaneous reformation of the tyrosyl radical. The NrdI* flavodoxin may play a more direct role in ribonucleotide reduction by the NrdF*I*E* system. We discuss the possibility that the nrdF*I*E* operon has been horizontally transferred to S. pyogenes from Mycoplasma spp.

Sign in / Sign up

Export Citation Format

Share Document