In vitro generation of ribonucleotide reductase with altered sensitivity to the inhibitors hydroxyurea and deoxynucleoside triphosphates

1981 ◽  
Vol 1 (8) ◽  
pp. 627-633 ◽  
Author(s):  
Atsushi Sato ◽  
Joseph G. Cory
Keyword(s):  
Ribonucleotide Reductase ◽  
Altered Sensitivity

scholarly journals In vitro activities of novel catecholate siderophores against Plasmodium falciparum.

1996 ◽  
Vol 40 (9) ◽  
pp. 2094-2098 ◽  
Author(s):  
B Pradines ◽  
F Ramiandrasoa ◽  
L K Basco ◽  
L Bricard ◽  
G Kunesch ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Mechanism Of Action ◽  
Ribonucleotide Reductase ◽  
Antimalarial Activity ◽  
Iron Chelators ◽  
Resistant Clone ◽  
Iron Deprivation ◽  
Level Of Activity ◽  
Susceptible Clone

The activities of novel iron chelators, alone and in combination with chloroquine, quinine, or artemether, were evaluated in vitro against susceptible and resistant clones of Plasmodium falciparum with a semimicroassay system. N4-nonyl,N1,N8-bis(2,3-dihydroxybenzoyl) spermidine hydrobromide (compound 7) demonstrated the highest level of activity: 170 nM against a chloroquine-susceptible clone and 1 microM against a chloroquine-resistant clone (50% inhibitory concentrations). Compounds 6, 8, and 10 showed antimalarial activity with 50% inhibitory concentrations of about 1 microM. Compound 7 had no effect on the activities of chloroquine, quinine, and artemether against either clone, and compound 8 did not enhance the schizontocidal action of either chloroquine or quinine against the chloroquine-resistant clone. The incubation of compound 7 with FeCI3 suppressed or decreased the in vitro antimalarial activity of compound 7, while no effect was observed with incubation of compound 7 with CuSO4 and ZnSO4. These results suggest that iron deprivation may be the main mechanism of action of compound 7 against the malarial parasites. Chelator compounds 7 and 8 primarily affected trophozoite stages, probably by influencing the activity of ribonucleotide reductase, and thus inhibiting DNA synthesis.

scholarly journals Investigation of in Vivo Roles of the C-terminal Tails of the Small Subunit (ββ′) of Saccharomyces cerevisiae Ribonucleotide Reductase

2013 ◽  
Vol 288 (20) ◽  
pp. 13951-13959 ◽  
Author(s):  
Yan Zhang ◽  
Xiuxiang An ◽  
JoAnne Stubbe ◽  
Mingxia Huang
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ribonucleotide Reductase ◽  
Large Subunit ◽  
Small Subunit ◽  
Cluster Assembly ◽  
E Coli ◽  
Viability Assay ◽  
Docking Model

The small subunit (β2) of class Ia ribonucleotide reductase (RNR) houses a diferric tyrosyl cofactor (Fe2III-Y•) that initiates nucleotide reduction in the large subunit (α2) via a long range radical transfer (RT) pathway in the holo-(α2)m(β2)n complex. The C-terminal tails of β2 are predominantly responsible for interaction with α2, with a conserved tyrosine residue in the tail (Tyr356 in Escherichia coli NrdB) proposed to participate in cofactor assembly/maintenance and in RT. In the absence of structure of any holo-RNR, the role of the β tail in cluster assembly/maintenance and its predisposition within the holo-complex have remained unknown. In this study, we have taken advantage of the unusual heterodimeric nature of the Saccharomyces cerevisiae RNR small subunit (ββ′), of which only β contains a cofactor, to address both of these issues. We demonstrate that neither β-Tyr376 nor β′-Tyr323 (Tyr356 equivalent in NrdB) is required for cofactor assembly in vivo, in contrast to the previously proposed mechanism for E. coli cofactor maintenance and assembly in vitro. Furthermore, studies with reconstituted-ββ′ and an in vivo viability assay show that β-Tyr376 is essential for RT, whereas Tyr323 in β′ is not. Although the C-terminal tail of β′ is dispensable for cofactor formation and RT, it is essential for interactions with β and α to form the active holo-RNR. Together the results provide the first evidence of a directed orientation of the β and β′ C-terminal tails relative to α within the holoenzyme consistent with a docking model of the two subunits and argue against RT across the β β′ interface.

scholarly journals The Novel Ribonucleotide Reductase Inhibitor COH29 Inhibits DNA Repair In Vitro

2015 ◽  
Vol 87 (6) ◽  
pp. 996-1005 ◽  
Author(s):  
Mei-Chuan Chen ◽  
Bingsen Zhou ◽  
Keqiang Zhang ◽  
Yate-Ching Yuan ◽  
Frank Un ◽  
...  
Keyword(s):  
Dna Repair ◽  
Ribonucleotide Reductase ◽  
Reductase Inhibitor ◽  
The Novel ◽  
Ribonucleotide Reductase Inhibitor

scholarly journals Identification of Ribonucleotide Reductase Protein R1 as an Activator of Microtubule Nucleation in Xenopus Egg Mitotic Extracts

2000 ◽  
Vol 11 (12) ◽  
pp. 4173-4187 ◽  
Author(s):  
Saeko Takada ◽  
Takehiko Shibata ◽  
Yasushi Hiraoka ◽  
Hirohisa Masuda
Keyword(s):  
Ribonucleotide Reductase ◽  
Large Subunit ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Microtubule Nucleation ◽  
Pole Body ◽  
Recombinant Mouse ◽  
Xenopus Egg ◽  
Essential Subunit

Microtubule nucleation on the centrosome and the fungal equivalent, the spindle pole body (SPB), is activated at the onset of mitosis. We previously reported that mitotic extracts prepared fromXenopus unfertilized eggs convert the interphase SPB of fission yeast into a competent state for microtubule nucleation. In this study, we have purified an 85-kDa SPB activator from the extracts and identified it as the ribonucleotide reductase large subunit R1. We further confirmed that recombinant mouse R1 protein was also effective for SPB activation. On the other hand, another essential subunit of ribonucleotide reductase, R2 protein, was not required for SPB activation. SPB activation by R1 protein was suppressed in the presence of anti-R1 antibodies or a partial oligopeptide of R1; the oligopeptide also inhibited aster formation on Xenopussperm centrosomes. In accordance, R1 was detected in animal centrosomes by immunofluorescence and immunoblotting with anti-R1 antibodies. In addition, recombinant mouse R1 protein bound to γ- and α/β-tubulin in vitro. These results suggest that R1 is a bifunctional protein that acts on both ribonucleotide reduction and centrosome/SPB activation.

scholarly journals Altered Ribonucleotide Reductase Obtained by in vitro Mutagenesis of Cloned Escherichia coli DNA.

1981 ◽  
Vol 35b ◽  
pp. 143-144
Author(s):  
Anton Platz ◽  
Joseph W. DePierre ◽  
Klaus Mosbach ◽  
Gian Maria Pacifici ◽  
Anders Rane
Keyword(s):  
Escherichia Coli ◽  
Ribonucleotide Reductase ◽  
In Vitro Mutagenesis

Deoxyribonucleotide Synthesis in Phycovirus-Infected Green Algae. A New Virus-Induced Ribonucleotide Reductase

1993 ◽  
Vol 48 (1-2) ◽  
pp. 113-118 ◽  
Author(s):  
Claus Bornemann ◽  
Hartmut Follmann
Keyword(s):  
Green Algae ◽  
Ribonucleotide Reductase ◽  
Fold Increase ◽  
Optimum Concentration ◽  
Characteristic Parameters ◽  
Temperature Optimum ◽  
Allosteric Effector ◽  
Cell Extracts ◽  
Key Enzyme

Infection of Chlorella-like green algae with freshwater phycoviruses is associated with a large and rapid demand for DNA precursors which cannot be met by the algal deoxyribonucleotide-synthesizing enzymes. We have demonstrated in these cells an up to ten-fold increase of the key enzyme, ribonucleotide reductase, 1-2 h post infection. The enzyme activity has been partially enriched from cell extracts. In vitro, it differs from that of uninfected algae in three characteristic parameters, viz. eight-fold higher resistance to millimolar hydroxyurea concentrations, much higher optimum concentration of an allosteric effector nucleotide, thymidine triphosphate, and an unusually low temperature optimum at 20 °C. We conclude that the large DNA phycoviruses, like Herpes and pox viruses, code for their own specific ribonucleotide reductase.

Genetic polymorphisms of the adenosine triphosphate-binding cassette transporters (ABCC2, ABCG2) and irinotecan toxicity in cancer patients

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 13096-13096
Author(s):  
M. Usui ◽  
M. Ando ◽  
C. Kitagawa ◽  
Y. Ando ◽  
Y. Sekido ◽  
...  
Keyword(s):  
Cancer Patients ◽  
Adenosine Triphosphate ◽  
Interindividual Variability ◽  
Antitumor Drugs ◽  
Severe Toxicity ◽  
Reference Allele ◽  
Reference Type ◽  
Grade 3 ◽  
Altered Sensitivity

13096 Background: Irinotecan is subject to substantial interindividual variability in pharmacokinetic and the occurrence of unpredictably severe toxicities of leukopenia or diarrhea. These toxicities have been reported to be associated with increased levels of SN-38, the active metabolite of irinotecan. ABCC2 and ABCG2, members of adenosine triphosphate-binding cassette transporters, are involved in mediating the elimination of anionic antitumor drugs, such as SN-38 and SN-38G. Recently, Innocenti et al. reported SN-38G AUC and SN-38G/SN-38 AUC ratios were correlated with ABCC2 3972T>C. The variant ABCG2 421C>A was associated with low ABCG2 expression levels and altered sensitivity to several drugs, including SN-38, in vitro as compared with the reference-type protein. Methods: We assessed whether the variants ABCC2 3972T>C and ABCG2 421C>A would be associated with severe toxicity (leucopenia of grade 4 and/or diarrhea of grade 3 or worse) in 120 Japanese cancer patients in which 27 patients experienced severe toxicity. Results: 74 patients (62%) were homozygotes for the reference allele of ABCC2 3972T>C, 39 heterozygous (33%), and 7 homozygous (6%) for the variant, whereas 62 patients (52%) were homozygous for the reference allele of ABCG2 421C>A, 48 heterozygous (40%) and 10 homozygous (8%) for the variant. Logistic regression analysis did not show any significant associations between the occurrence of severe toxicity and carrying these variants (see Table ). Conclusions: It suggests that genotyping of ABCC2 3972T>C and ABCG2 421C>A would not be useful for predicting severe toxicity caused by irinotecan. [Table: see text] No significant financial relationships to disclose.

Expression of ribonucleotide reductase M2 subunit in gastric cancer and effects of RRM2 inhibition in vitro

2010 ◽  
Vol 41 (12) ◽  
pp. 1742-1748 ◽  
Author(s):  
Teppei Morikawa ◽  
Rumi Hino ◽  
Hiroshi Uozaki ◽  
Daichi Maeda ◽  
Tetsuo Ushiku ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Ribonucleotide Reductase

scholarly journals In Vivo Assay for Low-Activity Mutant Forms of Escherichia coli Ribonucleotide Reductase

2003 ◽  
Vol 185 (4) ◽  
pp. 1167-1173 ◽  
Author(s):  
Monica Ekberg ◽  
Pernilla Birgander ◽  
Britt-Marie Sjöberg
Keyword(s):  
Escherichia Coli ◽  
Ribonucleotide Reductase ◽  
Active Site ◽  
Site Directed Mutagenesis ◽  
In Vitro Assays ◽  
Tyrosyl Radical ◽  
In Vivo Assay ◽  
Radical Transfer

ABSTRACT Ribonucleotide reductase (RNR) catalyzes the essential production of deoxyribonucleotides in all living cells. In this study we have established a sensitive in vivo assay to study the activity of RNR in aerobic Escherichia coli cells. The method is based on the complementation of a chromosomally encoded nonfunctional RNR with plasmid-encoded RNR. This assay can be used to determine in vivo activity of RNR mutants with activities beyond the detection limits of traditional in vitro assays. E. coli RNR is composed of two homodimeric proteins, R1 and R2. The R2 protein contains a stable tyrosyl radical essential for the catalysis that takes place at the R1 active site. The three-dimensional structures of both proteins, phylogenetic studies, and site-directed mutagenesis experiments show that the radical is transferred from the R2 protein to the active site in the R1 protein via a radical transfer pathway composed of at least nine conserved amino acid residues. Using the new assay we determined the in vivo activity of mutants affecting the radical transfer pathway in RNR and identified some residual radical transfer activity in two mutant R2 constructs (D237N and W48Y) that had previously been classified as negative for enzyme activity. In addition, we show that the R2 mutant Y356W is completely inactive, in sharp contrast to what has previously been observed for the corresponding mutation in the mouse R2 enzyme.

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