期刊
BIOCHEMISTRY
卷 50, 期 25, 页码 5615-5623出版社
AMER CHEMICAL SOC
DOI: 10.1021/bi200348q
关键词
-
资金
- National Institutes of Health [GM81393]
Bacillus subtilis class Ib ribonucleotide reductase (RNR) catalyzes the conversion of nucleotides to deoxynudeotides, providing the building blocks for DNA replication and repair. It is composed of two proteins: alpha (NrdE) and beta (NrdF). beta contains the metallo-cofactor, essential for the initiation of the reduction process. The RNR genes are organized within the nrdI-nrdE-nrdF-ymaB operon. Each protein has been cloned, expressed, and purified from Escherichia coli. As isolated, recombinant NrdF (rNrdF) contained a diferric-tyrosyl radical [Fe(III)(2)-Y-center dot] cofactor. Alternatively, this cluster could be self-assembled from apo-rNrdF, Fe(II), and O-2. Apo-rNrdF loaded using 4 Mn(II)/beta(2),O-2, and reduced NrdI (a flavodoxin) can form a dimanganese-(III)-Y-center dot [Mn(III)(2)-Y-center dot] cofactor. In the presence of rNrdE, ATP, and CDP, Mn(III)(2)-Y-center dot and Fe(III)(2)-Y-center dot rNrdF generate dCDP at rates of 132 and 10 nmol min(-1) mg(-1), respectively (both normalized for 1 Y-center dot/beta(2)). To determine the endogenous cofactor of NrdF in B. subtilis, the entire operon was placed behind a Pspank(hy) promoter and integrated into the B. subtilis genome at the amyE site. All four genes were induced in cells grown in Luria-Bertani medium, with levels of NrdE and NrdF elevated 35-fold relative to that of the wild-type strain. NrdE and NrdF were copurified in a 1:1 ratio from this engineered B. subtilis. The visible, EPR, and atomic absorption spectra of the purified NrdENrdF complex (eNrdF) exhibited characteristics of a Mn(III)(2)-Y-center dot center with 2 Mn/beta(2) and 0.5 Y-center dot/beta(2) and an activity of 318-363 nmol min(-1) mg(-1) (normalized for 1 Y-center dot/beta(2)). These data strongly suggest that the B. subtilis class Ib RNR is a Mn(III)(2)-Y-center dot enzyme.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据