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Biochemistry Sep 2022is the causative parasitic protozoan of the disease trichomoniasis, the most prevalent, nonviral sexually transmitted disease in the world. is a parasite that...
is the causative parasitic protozoan of the disease trichomoniasis, the most prevalent, nonviral sexually transmitted disease in the world. is a parasite that scavenges nucleosides from the host organism via catalysis by nucleoside hydrolase (NH) enzymes to yield purine and pyrimidine bases. One of the four NH enzymes identified within the genome of displays unique specificity toward purine nucleosides, adenosine and guanosine, but not inosine, and atypically shares greater sequence similarity to the pyrimidine hydrolases. Bioinformatic analysis of this enzyme, adenosine/guanosine-preferring nucleoside ribohydrolase (AGNH), was incapable of identifying the residues responsible for this uncommon specificity, highlighting the need for structural information. Here, we report the X-ray crystal structures of , unliganded AGNH and three additional structures of the enzyme bound to fragment and small-molecule inhibitors. Taken together, these structures facilitated the identification of residue Asp231, which engages in substrate interactions in the absence of those residues that typically support the canonical purine-specific tryptophan-stacking specificity motif. An altered substrate-binding pose is mirrored by repositioning within the protein scaffold of the His80 general acid/base catalyst. The newly defined structure-determined sequence markers allowed the assignment of additional NH orthologs, which are proposed to exhibit the same specificity for adenosine and guanosine alone and further delineate specificity classes for these enzymes.
Topics: Adenosine; Animals; Guanosine; Inosine; N-Glycosyl Hydrolases; Parasites; Pyrimidines; Substrate Specificity
PubMed: 35994320
DOI: 10.1021/acs.biochem.2c00361 -
Proceedings of the National Academy of... Sep 2023In the final step of cytokinin biosynthesis, the main pathway is the elimination of a ribose-phosphate moiety from the cytokinin nucleotide precursor by...
In the final step of cytokinin biosynthesis, the main pathway is the elimination of a ribose-phosphate moiety from the cytokinin nucleotide precursor by phosphoribohydrolase, an enzyme encoded by a gene named LONELY GUY (LOG). This reaction accounts for most of the cytokinin supply needed for regulating plant growth and development. In contrast, the LOG-independent pathway, in which dephosphorylation and deribosylation sequentially occur, is also thought to play a role in cytokinin biosynthesis, but the gene entity and physiological contribution have been elusive. In this study, we profiled the phytohormone content of chromosome segment substitution lines of and searched for genes affecting the endogenous levels of cytokinin ribosides by quantitative trait loci analysis. Our approach identified a gene encoding an enzyme that catalyzes the deribosylation of cytokinin nucleoside precursors and other purine nucleosides. The cytokinin/purine riboside nucleosidase 1 (CPN1) we identified is a cell wall-localized protein. Loss-of-function mutations () were created by inserting a -retrotransposon that altered the cytokinin composition in seedling shoots and leaf apoplastic fluid. The mutation also abolished cytokinin riboside nucleosidase activity in leaf extracts and attenuated the -zeatin riboside-responsive expression of cytokinin marker genes. Grain yield of the mutants declined due to altered panicle morphology under field-grown conditions. These results suggest that the cell wall-localized LOG-independent cytokinin activating pathway catalyzed by CPN1 plays a role in cytokinin control of rice growth. Our finding broadens our spatial perspective of the cytokinin metabolic system.
Topics: Oryza; Cytokinins; Purine Nucleosides; N-Glycosyl Hydrolases; Nucleosides; Cell Wall
PubMed: 37639600
DOI: 10.1073/pnas.2217708120 -
Microbiology Spectrum Aug 2022Toyocamycin (TM) is an adenosine-analog antibiotic isolated from Streptomyces toyocaensis. It inhibits Candida albicans, several plant fungal pathogens, and human cells,...
Toyocamycin (TM) is an adenosine-analog antibiotic isolated from Streptomyces toyocaensis. It inhibits Candida albicans, several plant fungal pathogens, and human cells, but many fungi, including Saccharomyces cerevisiae, are much less susceptible to TM. Aiming to clarify why TM and its analogs tubercidin and 5-iodotubercidin are active against C. albicans but not S. cerevisiae, this study focused on the absence of purine nucleoside transport activity from S. cerevisiae. When the concentrative nucleoside transporter (CNT) of C. albicans was expressed in S. cerevisiae, the recombinant strain became sensitive to TM and its analogs. The expression of C. albicans purine nucleoside permease in S. cerevisiae did not result in sensitivity to TM. Clustered regularly interspaced short palindromic repeat-mediated disruption of CNT was performed in C. albicans. The CNTΔ strain of C. albicans became insensitive to TM and its analogs. These data suggest that the toxicity of TM and its analogs toward C. albicans results from their transport via CNT. Interestingly, S. cerevisiae also became sensitive to TM and its analogs if human CNT3 was introduced into cells. These findings enhance our understanding of the mechanisms of action of adenosine analogs toward pathogens and human cells. We investigated the mechanism of toxicity of TM and its analogs to C. albicans. Inspired by the effect of the copresence of TM and purine nucleosides on cell growth of C. albicans, we investigated the involvement of CNT in the toxicity mechanism by expressing CNT of C. albicans (CaCNT) in S. cerevisiae and deleting CaCNT in C. albicans. Our examinations clearly demonstrated that CaCNT is responsible for the toxicity of TM to C. albicans. S. cerevisiae expressing the human ortholog of CaCNT also became sensitive to TM and its analogs, and the order of effects of the TM analogs was a little different between CaCNT- and hCNT3-expressing S. cerevisiae. These findings are beneficial for an understanding of the mechanisms of action of adenosine analogs toward pathogens and human cells and also the development of new antifungal drugs.
Topics: Adenosine; Candida albicans; Humans; Nucleoside Transport Proteins; Purine Nucleosides; Saccharomyces cerevisiae; Toyocamycin
PubMed: 35913167
DOI: 10.1128/spectrum.01138-22 -
The Journal of Organic Chemistry Jul 20202'-Deoxyguanosin-1-yl radical (dG(-H)) is the thermodynamically favored one-electron oxidation product of 2'-deoxyguanosine (dG), the most readily oxidized native...
2'-Deoxyguanosin-1-yl radical (dG(-H)) is the thermodynamically favored one-electron oxidation product of 2'-deoxyguanosine (dG), the most readily oxidized native nucleoside. dG(-H) is produced by the formal dehydration of a hydroxyl radical adduct of dG as well as by deprotonation of the corresponding radical cation. dG(-H) were formed as a result of the indirect and direct effects of ionizing radiation, among other DNA damaging agents. dG(-H) was generated photochemically (λ = 350 nm) from an -aryloxy-naphthalimide precursor (). The quantum yield for photochemical conversion of is ∼0.03 and decreases significantly in the presence O, suggesting that bond scission occurs from a triplet excited state. dG is formed quantitatively in the presence of excess β-mercaptoethanol. In the absence of a reducing agent, dG(-H) oxidizes , decreasing the dG yield to ∼50%. Addition of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) as a sacrificial reductant results in a quantitative yield of dG and two-electron oxidation products of 8-oxodGuo. -Aryloxy-naphthalimide is an efficient and high-yielding photochemical precursor of dG(-H) that will facilitate mechanistic studies on the reactivity of this important reactive intermediate involved in DNA damage.
Topics: 8-Hydroxy-2'-Deoxyguanosine; DNA Damage; Deoxyguanosine; Hydroxyl Radical; Oxidation-Reduction
PubMed: 32525316
DOI: 10.1021/acs.joc.0c01095 -
Biochemistry. Biokhimiia Dec 20178-Oxo-7,8-dihydroguanine (8-oxo-G) is a key biomarker of oxidative damage to DNA in cells, and its genotoxicity is well-studied. In recent years, it has been confirmed... (Review)
Review
8-Oxo-7,8-dihydroguanine (8-oxo-G) is a key biomarker of oxidative damage to DNA in cells, and its genotoxicity is well-studied. In recent years, it has been confirmed experimentally that free 8-oxo-G and molecules containing it are not merely inert products of DNA repair or degradation, but they are actively involved in intracellular signaling. In this review, data are systematized indicating that free 8-oxo-G and oxidized (containing 8-oxo-G) extracellular DNA function in the body as mediators of stress signaling and initiate inflammatory and immune responses to maintain homeostasis under the action of external pathogens, whereas exogenous 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGuo) exhibits pronounced antiinflammatory and antioxidant properties. This review describes known action mechanisms of oxidized guanine and 8-oxo-G-containing molecules. Prospects for their use as a therapeutic target are considered, as well as a pharmaceutical agent for treatment of a wide range of diseases whose pathogenesis is significantly contributed to by inflammation and oxidative stress.
Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Biomarkers; DNA Damage; DNA Repair; Deoxyguanosine; Guanine; Humans; Inflammation; Oxidative Stress
PubMed: 29523066
DOI: 10.1134/S0006297917130089 -
Expert Opinion on Pharmacotherapy Dec 2016Advances in acute lymphocytic leukemia (ALL) therapy has led to long-term survival rates in children. However, only 30%-40% of adults achieve long-term disease-free... (Review)
Review
Advances in acute lymphocytic leukemia (ALL) therapy has led to long-term survival rates in children. However, only 30%-40% of adults achieve long-term disease-free survival. After relapse, the outcome of salvage chemotherapy is very disappointing with less than 10% of long survival. Novel agents are therefore desperately required to improve response rates and survival, but also the quality of life of patients. Areas covered: The following review is a comprehensive summary of various novel options reported over the past few years in the therapeutic area of adult ALL. Expert opinion: Identifying key components involved in disease pathogenesis may lead to new approaches. In a near future, the incorporation of monoclonal antibodies and T-cell directed approaches including blinatumomab and chimeric antigen receptor T cells may increase the cure rates and may reduce the need for intensive therapy.
Topics: Adenine Nucleotides; Adult; Antibodies, Monoclonal; Antineoplastic Agents; Arabinonucleosides; Clofarabine; Disease-Free Survival; Drug Discovery; Humans; Molecular Targeted Therapy; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Purine Nucleosides; Pyrimidinones; Quality of Life; Recurrence; Salvage Therapy
PubMed: 27759440
DOI: 10.1080/14656566.2016.1250884 -
The Journal of Organic Chemistry Jan 2022Among the C6-halo purine ribonucleosides, the readily accessible 6-chloro derivative has been known to undergo slow SAr reactions with amines, particularly aryl amines....
Among the C6-halo purine ribonucleosides, the readily accessible 6-chloro derivative has been known to undergo slow SAr reactions with amines, particularly aryl amines. In this work, we show that in 0.1 M AcOH in EtOH, aryl amines react quite efficiently at the C6-position of 2',3',5'-tri--(-BuMeSi)-protected 6-chloropurine riboside (6-ClP-riboside), with concomitant cleavage of the 5'-silyl group. These two-step processes proceeded in generally good yields, and notably, reactions in the absence of AcOH were much slower and/or lower yielding. Corresponding reactions of 2',3',5'-tri--(-BuMeSi)-protected 6-ClP-riboside with alkyl amines proceeded well but without desilylation at the primary hydroxyl terminus. These differences are likely due to the acidities of the ammonium chlorides formed in these reactions, and the role of AcOH was not desilylation but possibly only purine activation. With 50% aqueous TFA in THF at 0 °C, cleavage of the 5'-silyl group from 2',3',5'-tri--(-BuMeSi)-protected -alkyl adenosine derivatives and from 6-ClP-riboside was readily achieved. Reactions of the 5'-deprotected 6-ClP-riboside with alkyl amines proceeded in high yields and under mild conditions. Because these complementary methodologies yielded -aryl and -alkyl adenosine derivatives containing a free 5'-hydroxyl group, a variety of product functionalizations were undertaken to yield ,C5'-doubly modified nucleoside analogues.
Topics: Adenosine; Amines; Hydroxyl Radical; Nucleosides; Water
PubMed: 34905365
DOI: 10.1021/acs.joc.1c01587 -
Organic Letters Oct 20223-(2-Deoxy-β-d-erythropentofuranosyl)pyrimido[1,2-]purin-10(3)-one (MdG) is an endogenous DNA adduct in bacterial and mammalian cells that could be explored as a...
3-(2-Deoxy-β-d-erythropentofuranosyl)pyrimido[1,2-]purin-10(3)-one (MdG) is an endogenous DNA adduct in bacterial and mammalian cells that could be explored as a biomarker for oxidative stress. Nonetheless, the lack of an efficient methodology for the preparation of MdG hampers the deep investigation of its biosynthesis and biorelevant processes. In this project, we aimed to address this issue by developing a highly efficient method to synthesize MdG and its analogues. This method has wide functional group tolerance, as various guanine-based nucleosides and nucleotides are suitable for the reaction. Furthermore, large-scale and derivatization reactions were carried out to showcase the possibility for biochemists to study DNA damage and repair processes in the future.
Topics: Animals; Nucleosides; Nucleotides; Guanine; Cyclization; Purine Nucleosides; Mammals
PubMed: 36255100
DOI: 10.1021/acs.orglett.2c03252 -
International Journal of Molecular... Jan 2023The guanine base in nucleic acids is, among the other bases, the most susceptible to being converted into 8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) when exposed to... (Review)
Review
The guanine base in nucleic acids is, among the other bases, the most susceptible to being converted into 8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) when exposed to reactive oxygen species. In double-helix DNA, 8-oxodG can pair with adenine; hence, it may cause a G > T (C > A) mutation; it is frequently referred to as a form of DNA damage and promptly corrected by DNA repair mechanisms. Moreover, 8-oxodG has recently been redefined as an epigenetic factor that impacts transcriptional regulatory elements and other epigenetic modifications. It has been proposed that 8-oxodG exerts epigenetic control through interplay with the G-quadruplex (G4), a non-canonical DNA structure, in transcription regulatory regions. In this review, we focused on the epigenetic roles of 8-oxodG and the G4 and explored their interplay at the genomic level.
Topics: 8-Hydroxy-2'-Deoxyguanosine; Deoxyguanosine; DNA Damage; DNA Repair; DNA
PubMed: 36768357
DOI: 10.3390/ijms24032031 -
Molecular BioSystems Nov 2014The 8-azapurines, and their 7-deaza and 9-deaza congeners, represent a unique class of isosteric (isomorphic) analogues of the natural purines, frequently capable of... (Review)
Review
The 8-azapurines, and their 7-deaza and 9-deaza congeners, represent a unique class of isosteric (isomorphic) analogues of the natural purines, frequently capable of substituting for the latter in many biochemical processes. Particularly interesting is their propensity to exhibit pH-dependent room-temperature fluorescence in aqueous medium, and in non-polar media. We herein review the physico-chemical properties of this class of compounds, with particular emphasis on the fluorescence emission properties of their neutral and/or ionic species, which has led to their widespread use as fluorescent probes in enzymology, including enzymes involved in purine metabolism, agonists/antagonists of adenosine receptors, mechanisms of catalytic RNAs, RNA editing, etc. They are also exceptionally useful fluorescent probes for analytical and clinical applications in crude cell homogenates.
Topics: Enzymes; Fluorescent Dyes; Humans; Models, Molecular; Nucleic Acids; Purine Nucleosides; Purine Nucleotides; Purines; Spectrometry, Fluorescence
PubMed: 25124808
DOI: 10.1039/c4mb00233d