1
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Were E, Viljoen A, Rasche F. Iron necessity for chlamydospore germination in Fusarium oxysporum f. sp. cubense TR4. Biometals 2023; 36:1295-1306. [PMID: 37380939 PMCID: PMC10684721 DOI: 10.1007/s10534-023-00519-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 06/19/2023] [Indexed: 06/30/2023]
Abstract
Fusarium wilt disease of banana, caused by the notorious soil-borne pathogen Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4), is extremely difficult to manage. Manipulation of soil pH or application of synthetic iron chelators can suppress the disease through iron starvation, which inhibits the germination of pathogen propagules called chlamydospores. However, the effect of iron starvation on chlamydospore germination is largely unknown. In this study, scanning electron microscopy was used to assemble the developmental sequence of chlamydospore germination and to assess the effect of iron starvation and pH in vitro. Germination occurs in three distinct phenotypic transitions (swelling, polarized growth, outgrowth). Outgrowth, characterized by formation of a single protrusion (germ tube), occurred at 2 to 3 h, and a maximum value of 69.3% to 76.7% outgrowth was observed at 8 to 10 h after germination induction. Germination exhibited plasticity with pH as over 60% of the chlamydospores formed a germ tube between pH 3 and pH 11. Iron-starved chlamydospores exhibited polarized-growth arrest, characterized by the inability to form a germ tube. Gene expression analysis of rnr1 and rnr2, which encode the iron-dependent enzyme ribonucleotide reductase, showed that rnr2 was upregulated (p < 0.0001) in iron-starved chlamydospores compared to the control. Collectively, these findings suggest that iron and extracellular pH are crucial for chlamydospore germination in Foc TR4. Moreover, inhibition of germination by iron starvation may be linked to a different mechanism, rather than repression of the function of ribonucleotide reductase, the enzyme that controls growth by regulation of DNA synthesis.
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Affiliation(s)
- Evans Were
- Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, 70599, Stuttgart, Germany
| | - Altus Viljoen
- Department of Plant Pathology, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - Frank Rasche
- Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), University of Hohenheim, 70599, Stuttgart, Germany.
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2
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Yin J, Wang X, Ge X, Ding F, Shi Z, Ge Z, Huang G, Zhao N, Chen D, Zhang J, Agnihotri S, Cao Y, Ji J, Lin F, Wang Q, Zhou Q, Wang X, You Y, Lu Z, Qian X. Hypoxanthine phosphoribosyl transferase 1 metabolizes temozolomide to activate AMPK for driving chemoresistance of glioblastomas. Nat Commun 2023; 14:5913. [PMID: 37737247 PMCID: PMC10516874 DOI: 10.1038/s41467-023-41663-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 09/13/2023] [Indexed: 09/23/2023] Open
Abstract
Temozolomide (TMZ) is a standard treatment for glioblastoma (GBM) patients. However, TMZ has moderate therapeutic effects due to chemoresistance of GBM cells through less clarified mechanisms. Here, we demonstrate that TMZ-derived 5-aminoimidazole-4-carboxamide (AICA) is converted to AICA ribosyl-5-phosphate (AICAR) in GBM cells. This conversion is catalyzed by hypoxanthine phosphoribosyl transferase 1 (HPRT1), which is highly expressed in human GBMs. As the bona fide activator of AMP-activated protein kinase (AMPK), TMZ-derived AICAR activates AMPK to phosphorylate threonine 52 (T52) of RRM1, the catalytic subunit of ribonucleotide reductase (RNR), leading to RNR activation and increased production of dNTPs to fuel the repairment of TMZ-induced-DNA damage. RRM1 T52A expression, genetic interruption of HPRT1-mediated AICAR production, or administration of 6-mercaptopurine (6-MP), a clinically approved inhibitor of HPRT1, blocks TMZ-induced AMPK activation and sensitizes brain tumor cells to TMZ treatment in mice. In addition, HPRT1 expression levels are positively correlated with poor prognosis in GBM patients who received TMZ treatment. These results uncover a critical bifunctional role of TMZ in GBM treatment that leads to chemoresistance. Our findings underscore the potential of combined administration of clinically available 6-MP to overcome TMZ chemoresistance and improve GBM treatment.
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Affiliation(s)
- Jianxing Yin
- Department of Neurosurgery, The First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
- Gusu School, Nanjing Medical University, 215006, Suzhou, China
| | - Xiefeng Wang
- Department of Neurosurgery, The First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
| | - Xin Ge
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
- Department of Nutrition and Food Hygiene, School of Public Health, Nanjing Medical University, 210029, Nanjing, China
| | - Fangshu Ding
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
- Department of Nutrition and Food Hygiene, School of Public Health, Nanjing Medical University, 210029, Nanjing, China
| | - Zhumei Shi
- Department of Neurosurgery, The First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
| | - Zehe Ge
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
- Department of Nutrition and Food Hygiene, School of Public Health, Nanjing Medical University, 210029, Nanjing, China
| | - Guang Huang
- Department of Health Inspection and Quarantine, School of Public Health, Nanjing Medical University, 211166, Nanjing, China
| | - Ningwei Zhao
- China Exposomics Institute, 200120, Shanghai, China
- Affiliated Hospital of Nanjing University of Chinese Medicine, 210029, Nanjing, China
| | - Dongyin Chen
- Department of Medicinal Chemistry, School of Pharmacy, Nanjing Medical University, 211166, Nanjing, China
| | - Junxia Zhang
- Department of Neurosurgery, The First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
| | - Sameer Agnihotri
- Department of Neurological Surgery, UPMC Children's Hospital of Pittsburgh, Pittsburgh, PA, 15224, USA
| | - Yuandong Cao
- Department of Radiation Oncology, The First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
| | - Jing Ji
- Department of Neurosurgery, The First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
| | - Fan Lin
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
- Department of Cell Biology, School of Basic Medical Sciences, Nanjing Medical University, 211166, Nanjing, China
| | - Qianghu Wang
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
- Department of Bioinformatics, Nanjing Medical University, 211166, Nanjing, China
| | - Qigang Zhou
- Department of Clinical Pharmacology, School of Pharmacy, Nanjing Medical University, 211166, Nanjing, China
| | - Xiuxing Wang
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China
- Department of Cell Biology, School of Basic Medical Sciences, Nanjing Medical University, 211166, Nanjing, China
- National Health Commission Key Laboratory of Antibody Technologies, Nanjing Medical University, 211166, Nanjing, China
| | - Yongping You
- Department of Neurosurgery, The First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China.
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China.
| | - Zhimin Lu
- Zhejiang Provincial Key Laboratory of Pancreatic Disease, The First Affiliated Hospital, Zhejiang University School of Medicine, 310029, Hangzhou, China.
- Institute of Translational Medicine, Zhejiang University Cancer Center, Zhejiang University, 310029, Hangzhou, China.
| | - Xu Qian
- Department of Neurosurgery, The First Affiliated Hospital of Nanjing Medical University, 210029, Nanjing, China.
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, 211166, Nanjing, China.
- Department of Nutrition and Food Hygiene, School of Public Health, Nanjing Medical University, 210029, Nanjing, China.
- Key Laboratory of Modern Toxicology of Ministry of Education, School of Public Health, Nanjing Medical University, 211166, Nanjing, China.
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Croushore EE, Koppenhafer SL, Goss KL, Geary EL, Gordon DJ. Activator Protein-1 (AP-1) Signaling Inhibits the Growth of Ewing Sarcoma Cells in Response to DNA Replication Stress. Cancer Res Commun 2023; 3:1580-1593. [PMID: 37599787 PMCID: PMC10434289 DOI: 10.1158/2767-9764.crc-23-0268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 07/11/2023] [Accepted: 07/13/2023] [Indexed: 08/22/2023]
Abstract
Ribonucleotide reductase (RNR) catalyzes the rate-limiting step in the synthesis of deoxyribonucleosides and is required for DNA replication. Multiple types of cancer, including Ewing sarcoma tumors, are sensitive to RNR inhibitors or a reduction in the levels of either the RRM1 or RRM2 subunits of RNR. However, the polypharmacology and off-target effects of RNR inhibitors have complicated the identification of the mechanisms that regulate sensitivity and resistance to this class of drugs. Consequently, we used a conditional knockout (CRISPR/Cas9) and rescue approach to target RRM1 in Ewing sarcoma cells and identified that loss of the RRM1 protein results in the upregulation of the expression of multiple members of the activator protein-1 (AP-1) transcription factor complex, including c-Jun and c-Fos, and downregulation of c-Myc. Notably, overexpression of c-Jun and c-Fos in Ewing sarcoma cells is sufficient to inhibit cell growth and downregulate the expression of the c-Myc oncogene. We also identified that the upregulation of AP-1 is mediated, in part, by SLFN11, which is a replication stress response protein that is expressed at high levels in Ewing sarcoma. In addition, small-molecule inhibitors of RNR, including gemcitabine, and histone deacetylase inhibitors, which reduce the level of the RRM1 protein, also activate AP-1 signaling and downregulate the level of c-Myc in Ewing sarcoma. Overall, these results provide novel insight into the critical pathways activated by loss of RNR activity and the mechanisms of action of inhibitors of RNR. Significance RNR is the rate-limiting enzyme in the synthesis of deoxyribonucleotides. Although RNR is the target of multiple chemotherapy drugs, polypharmacology and off-target effects have complicated the identification of the precise mechanism of action of these drugs. In this work, using a knockout-rescue approach, we identified that inhibition of RNR upregulates AP-1 signaling and downregulates the level of c-Myc in Ewing sarcoma tumors.
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Affiliation(s)
- Emma E. Croushore
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Iowa, Iowa City, Iowa
| | - Stacia L. Koppenhafer
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Iowa, Iowa City, Iowa
| | - Kelli L. Goss
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Iowa, Iowa City, Iowa
| | - Elizabeth L. Geary
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Iowa, Iowa City, Iowa
| | - David J. Gordon
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Iowa, Iowa City, Iowa
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4
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Andree GA, Feliciano PR, Kang G, Levitz TS, Miller KR, Westmoreland DE, Drennan CL. Capturing Snapshots of Ribonucleotide Reductase Using Cryo-Electron Microscopy. Microsc Microanal 2023; 29:893. [PMID: 37613477 DOI: 10.1093/micmic/ozad067.441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Affiliation(s)
- Gisele A Andree
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Patricia R Feliciano
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, United States
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Gyunghoon Kang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Talya S Levitz
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Kelsey R Miller
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Dana E Westmoreland
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Catherine L Drennan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, United States
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, United States
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5
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Saeed A, Ejaz SA, Khalid A, Channar PA, Aziz M, Abbas Q, Wani TA, Alsaif NA, Alanazi MM, Al-Hossaini AM, Altwaijry N, Zargar S, Elhadi M, Hökelek T. Acetophenone-Based 3,4-Dihydropyrimidine-2(1H)-Thione as Potential Inhibitor of Tyrosinase and Ribonucleotide Reductase: Facile Synthesis, Crystal Structure, In-Vitro and In-Silico Investigations. Int J Mol Sci 2022; 23:13164. [PMID: 36361953 PMCID: PMC9658835 DOI: 10.3390/ijms232113164] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 10/24/2022] [Accepted: 10/27/2022] [Indexed: 08/09/2023] Open
Abstract
The acetophenone-based 3,4-dihydropyrimidine-2(1H)-thione was synthesized by the reaction of 4-methylpent-3-en-2-one (1), 4-acetyl aniline (2) and potassium thiocyanate. The spectroscopic analysis including: FTIR, 1H-NMR, and single crystal analysis proved the structure of synthesized compound (4), with the six-membered nonplanar ring in envelope conformation. In crystal structure, the intermolecular N-H ⋯ S and C-H ⋯ O hydrogen bonds link the molecule in a two-dimensional manner which is parallel to (010) the plane enclosing R22 (8) and R22 (10) ring motifs. After that, the Hirshfeld surfaces and their related two-dimensional fingerprint plots were used for thorough investigation of intermolecular interactions. According to Hirshfeld surface analysis, the most substantial contributions to the crystal packing are from H ⋯ H (59.5%), H ⋯ S/S ⋯ H (16.1%), and H ⋯ C/C ⋯ H (13.1%) interactions. The electronic properties and stability of the compound were investigated through density functional theory (DFT) studies using B3LYP functional and 6-31G* as a basis set. The compound 4 displayed the high chemical reactivity with chemical softness of 2.48. In comparison to the already reported known tyrosinase inhibitor, the newly synthesized derivatives exhibited almost seven-fold better inhibition of tyrosinase (IC50 = 1.97 μM), which was further supported by molecular docking studies. The compound 4 inside the active pocket of ribonucleotide reductase (RNR) exhibited a binding energy of -19.68 kJ/mol, and with mammalian deoxy ribonucleic acid (DNA) it acts as an effective DNA groove binder with a binding energy of -21.32 kJ/mol. The results suggested further exploration of this compound at molecular level to synthesize more potential leads for the treatment of cancer.
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Affiliation(s)
- Aamer Saeed
- Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
| | - Syeda Abida Ejaz
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
| | - Aqsa Khalid
- Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
| | - Pervaiz Ali Channar
- Department of Basic Sciences and Humanities, Faculty of of Information Science and Humanities, Dawood University of Engineering and Technology, Karachi 74800, Pakistan
| | - Mubashir Aziz
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
| | - Qamar Abbas
- Department of Biology, College of Science, University of Bahrain, Sakhir Campus, Zallaq 32038, Bahrain
- Department of Biological Sciences, College of Natural Sciences, Kongju National University, 56 Gongjudehak-Ro, Gongju 314-701, Chungnam, Korea
| | - Tanveer A. Wani
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia
| | - Nawaf A. Alsaif
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia
| | - Mohammed M. Alanazi
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia
| | - Abdullah M. Al-Hossaini
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia
| | - Nojood Altwaijry
- Department of Biochemistry, College of Science, King Saud University, P.O. Box 22452, Riyadh 11451, Saudi Arabia
| | - Seema Zargar
- Department of Biochemistry, College of Science, King Saud University, P.O. Box 22452, Riyadh 11451, Saudi Arabia
| | - Muawya Elhadi
- Department of Physics, Faculty of Science and Humanities, Ed Dawadmi, Shaqra University, Shaqra 11961, Saudi Arabia
| | - Tuncer Hökelek
- Department of Physics, Faculty of Engineering, Hacettepe University, Beytepe, Ankara 06800, Turkey
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6
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Islam MA, Barshetty MM, Srinivasan S, Dudekula DB, Rallabandi VPS, Mohammed S, Natarajan S, Park J. Identification of Novel Ribonucleotide Reductase Inhibitors for Therapeutic Application in Bile Tract Cancer: An Advanced Pharmacoinformatics Study. Biomolecules 2022; 12:biom12091279. [PMID: 36139117 PMCID: PMC9496582 DOI: 10.3390/biom12091279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 09/05/2022] [Accepted: 09/08/2022] [Indexed: 11/28/2022] Open
Abstract
Biliary tract cancer (BTC) is constituted by a heterogeneous group of malignant tumors that may develop in the biliary tract, and it is the second most common liver cancer. Human ribonucleotide reductase M1 (hRRM1) has already been proven to be a potential BTC target. In the current study, a de novo design approach was used to generate novel and effective chemical therapeutics for BTC. A set of comprehensive pharmacoinformatics approaches was implemented and, finally, seventeen potential molecules were found to be effective for the modulation of hRRM1 activity. Molecular docking, negative image-based ShaEP scoring, absolute binding free energy, in silico pharmacokinetics, and toxicity assessments corroborated the potentiality of the selected molecules. Almost all molecules showed higher affinity in comparison to gemcitabine and naphthyl salicylic acyl hydrazone (NSAH). On binding interaction analysis, a number of critical amino acids was found to hold the molecules at the active site cavity. The molecular dynamics (MD) simulation study also indicated the stability between protein and ligands. High negative MM-GBSA (molecular mechanics generalized Born and surface area) binding free energy indicated the potentiality of the molecules. Therefore, the proposed molecules might have the potential to be effective therapeutics for the management of BTC.
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Affiliation(s)
- Md Ataul Islam
- 3BIGS Omicscore Private Limited, 909 Lavelle Building, Richmond Circle, Bangalore 560025, India
| | | | - Sridhar Srinivasan
- 3BIGS Omicscore Private Limited, 909 Lavelle Building, Richmond Circle, Bangalore 560025, India
| | - Dawood Babu Dudekula
- 3BIGS Omicscore Private Limited, 909 Lavelle Building, Richmond Circle, Bangalore 560025, India
| | | | - Sameer Mohammed
- 3BIGS Omicscore Private Limited, 909 Lavelle Building, Richmond Circle, Bangalore 560025, India
| | | | - Junhyung Park
- 3BIGS Co., Ltd., B-831, Geumgang Penterium IX Tower, Hwaseong 18469, Korea
- Correspondence:
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Kirschner GK. Beyond the pale - uncovering the role of ribonucleotide reductases in Setaria chloroplast development. Plant J 2022; 111:623-624. [PMID: 35894703 DOI: 10.1111/tpj.15909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
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8
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Wang Y, Zheng X, Wang X, Zhang X, Guo P, Liu L, Mei S. [Clinical characteristics and genetic analysis of a Chinese pedigree affected with mitochondrial DNA depletion syndrome due to compound heterozygous variants of RRM2B gene]. Zhonghua Yi Xue Yi Chuan Xue Za Zhi 2022; 39:26-30. [PMID: 34964961 DOI: 10.3760/cma.j.cn511374-20201116-00799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
OBJECTIVE To analyze the clinical characteristics and pathogenic gene in a Chinese pedigree affected with mitochondrial DNA depletion syndrome 8A (MTDPS8A). METHODS Whole exome sequencing was carried out for the patient. Sanger sequencing was used to verify the results, and PolyPhen-2 and PROVEAN software were used to predict the impact of amino acid changes on the function of the protein. RESULTS The patient, a two-month-old female, was admitted to the hospital for poor milk intake and poor mental response. Her clinical manifestations included feeding difficulty, shortness of breath and low muscle tone. Auxiliary laboratory test indicated that the infant was underdeveloped with abnormal liver, kidney, and heart functions accompanied by hyperlacticacidemia. She responded poorly to treatment and eventually died. Sequencing revealed that the child has carried compound heterozygous missense variants of the RRM2B gene, namely c.16delA (p.R6Gfs*22) and c.175G>C (p.A59P), which were respectively inherited from her father and mother, and both were newly discovered pathologic variants. CONCLUSION The c.16delA and c.175G>C compound heterozygous variants of the RRM2B gene probably underlay the pathogenesis of MTDPS8A. Above finding has strengthened the understanding of the clinical feature and genetic etiology of this disease and expanded the mutation spectrum of the RRM2B gene.
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Affiliation(s)
- Yanhong Wang
- Henan Provincial Neurodevelopment Engineering Research Center for Children, Henan Provincial Key Laboratory for Children's Genetic and Metabolic Diseases, Children's Hospital Affiliated to Zhengzhou University, Henan Provincial Children's Hospital, Zhengzhou Children's Hospital, Zhengzhou, Henan 450018, China.
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9
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Abstract
Early embryonic development is characterized by rapid cleavage divisions, which impose significant constraints on metabolic pathways. In this issue, Song et al. (2017) show that Drosophila embryos synthesize a large fraction of nucleotides on the go and that negative feedback between dATP and ribonucleotide reductase ensures tight control of dNTP concentration.
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Affiliation(s)
- Patrick L Ferree
- Department of Cell Biology, Duke University Medical Center, Durham NC 27710, USA
| | - Stefano Di Talia
- Department of Cell Biology, Duke University Medical Center, Durham NC 27710, USA.
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10
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Tomter AB, Zoppellaro G, Schmitzberger F, Andersen NH, Barra AL, Engman H, Nordlund P, Andersson KK. HF-EPR, Raman, UV/VIS light spectroscopic, and DFT studies of the ribonucleotide reductase R2 tyrosyl radical from Epstein-Barr virus. PLoS One 2011; 6:e25022. [PMID: 21980375 PMCID: PMC3181257 DOI: 10.1371/journal.pone.0025022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 08/22/2011] [Indexed: 11/19/2022] Open
Abstract
Epstein-Barr virus (EBV) belongs to the gamma subfamily of herpes viruses, among the most common pathogenic viruses in humans worldwide. The viral ribonucleotide reductase small subunit (RNR R2) is involved in the biosynthesis of nucleotides, the DNA precursors necessary for viral replication, and is an important drug target for EBV. RNR R2 generates a stable tyrosyl radical required for enzymatic turnover. Here, the electronic and magnetic properties of the tyrosyl radical in EBV R2 have been determined by X-band and high-field/high-frequency electron paramagnetic resonance (EPR) spectroscopy recorded at cryogenic temperatures. The radical exhibits an unusually low g₁-tensor component at 2.0080, indicative of a positive charge in the vicinity of the radical. Consistent with these EPR results a relatively high C-O stretching frequency associated with the phenoxyl radical (at 1508 cm⁻¹) is observed with resonance Raman spectroscopy. In contrast to mouse R2, EBV R2 does not show a deuterium shift in the resonance Raman spectra. Thus, the presence of a water molecule as a hydrogen bond donor moiety could not be identified unequivocally. Theoretical simulations showed that a water molecule placed at a distance of 2.6 Å from the tyrosyl-oxygen does not result in a detectable deuterium shift in the calculated Raman spectra. UV/VIS light spectroscopic studies with metal chelators and tyrosyl radical scavengers are consistent with a more accessible dimetal binding/radical site and a lower affinity for Fe²⁺ in EBV R2 than in Escherichia coli R2. Comparison with previous studies of RNR R2s from mouse, bacteria, and herpes viruses, demonstrates that finely tuned electronic properties of the radical exist within the same RNR R2 Ia class.
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Affiliation(s)
- Ane B. Tomter
- Department of Molecular Biosciences, University of Oslo, Oslo, Norway
| | | | - Florian Schmitzberger
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
| | - Niels H. Andersen
- Department of Molecular Biosciences, University of Oslo, Oslo, Norway
| | - Anne-Laure Barra
- Laboratoire National des Champs Magnétiques Intenses, LNCMI-G, UPR 3228, CNRS, Grenoble, France
| | - Henrik Engman
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
| | - Pär Nordlund
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
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11
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Ohno K, Tanaka-Azuma Y, Yoneda Y, Yamada T. Genotoxicity test system based on p53R2 gene expression in human cells: examination with 80 chemicals. Mutat Res 2005; 588:47-57. [PMID: 16236544 DOI: 10.1016/j.mrgentox.2005.09.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2005] [Revised: 09/13/2005] [Accepted: 09/16/2005] [Indexed: 11/20/2022]
Abstract
p53R2, which encodes a subunit of ribonucleotide reductase, is activated by DNA damage induced by gamma-ray and ultraviolet irradiation, and also by genotoxic chemicals such as adriamycin. For the purpose of constructing an easy-operating genotoxicity test system using human cell lines, we developed a p53R2-dependent luciferase reporter gene assay, and demonstrated dose-dependent luminescence caused by adriamycin in two human cell lines that express wild-type p53, MCF-7 and HepG2. The performance of this assay system was evaluated with 80 chemicals including those known in the Ames test as genotoxic or non-genotoxic. When the luciferase activity of cells treated with the test sample was over 200% to that of control cells in a dose-dependent increasing manner, the sample was judged positive as a genotoxic chemical. Forty of 43 Ames-positive chemicals induced luciferase activity in this assay system. Eight Ames-negative chemicals also induced luciferase activity. These eight chemicals are genotoxic in other in vitro test systems using mammalian cells. It is suggested that this assay system can be applied to rapid screening of chemicals for potential human genotoxicity.
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Affiliation(s)
- Katsutoshi Ohno
- Food Safety Research Institute, Nissin Food Products Co. Ltd, 2247 Noji-Cho, Kusatsu, Shiga 525-0055, Japan.
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12
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Gescher AJ, Steward WP. Relationship between mechanisms, bioavailibility, and preclinical chemopreventive efficacy of resveratrol: a conundrum. Cancer Epidemiol Biomarkers Prev 2003; 12:953-7. [PMID: 14578128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023] Open
Affiliation(s)
- Andreas J Gescher
- Cancer Biomarkers and Prevention Research Group, Department of Oncology, University of Leicester, Leicester LE2 7LX, United Kingdom.
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Maqbool Z, Kersey PJ, Fantes PA, McInerny CJ. MCB-mediated regulation of cell cycle-specific cdc22+ transcription in fission yeast. Mol Genet Genomics 2003; 269:765-75. [PMID: 12898217 DOI: 10.1007/s00438-003-0885-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2003] [Accepted: 06/09/2003] [Indexed: 10/26/2022]
Abstract
The cdc22+ gene of the fission yeast, Schizosaccharomyces pombe, encodes the large subunit of ribonucleotide reductase, and is periodically expressed during the mitotic cell cycle, transcript abundance reaching a maximum at the G1-S boundary. This regulation of expression is controlled by a transcription factor complex called DSC1, which binds to MCB motifs (ACGCGT) present in the promoter of cdc22+. cdc22+ has a complex pattern of MCBs, including two clusters of four motifs each, one of which is located within the transcribed region. We show that both clusters of MCBs contribute to the regulation of cdc22+ expression during the cell cycle, each having a different role. The MCB cluster within the transcribed region has the major role in regulating cdc22+, as its removal results in loss of transcription. The upstream cluster, instead, controls cell cycle-specific transcription through a negative function, as its removal results in expression of cdc22+ throughout the cell cycle. Both MCB clusters bind DSC1. We show that the interaction of DSC1 with the MCB cluster within the transcribed region has a high "on-off" rate, suggesting a mechanism by which DSC1 could activate expression, and still allow RNA polymerase to pass during transcription. Finally, we show that both clusters are orientation-dependent in their function. The significance of these results, in the context of MCB-mediated regulation of G1-S expression in fission yeast, is discussed.
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Affiliation(s)
- Z Maqbool
- Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, Scotland
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14
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Abstract
Two classes of enzymatic mechanisms that proceed by free radical chemistry initiated by the 5'-deoxyadenosyl radical are discussed. In the first class, the mechanism of the interconversion of L-lysine and L-beta-lysine catalyzed by lysine 2,3-aminomutase (LAM) involves four radicals, three of which have been spectroscopically characterized. The reversible formation of the 5'-deoxyadenosyl radical takes place by the chemical cleavage of S-adenosylmethionine (SAM) reacting with the [4Fe-4S]+ center in LAM. In other reactions of SAM with iron-sulfur proteins, SAM is irreversibly consumed to generate the 5'-deoxyadenosyl radical, which activates an enzyme by abstracting a hydrogen atom from an enzymatic glycyl residue to form a glycyl radical. The glycyl radical enzymes include pyruvate formate-lyase, anaerobic ribonucleotide reductase from Escherichia coli, and benzylsuccinate synthase. Biotin synthase and lipoate synthase are SAM-dependent [4Fe-4S] proteins that catalyze the insertion of sulfur into unactivated C-H bonds, which are cleaved by the 5'-deoxyadenosyl radical from SAM. In the second class of enzymatic mechanisms using free radicals, adenosylcobalamin-dependent reactions, the 5'-deoxyadenosyl radical arises from homolytic cleavage of the cobalt-carbon bond, and it initiates radical reactions by abstracting hydrogen atoms from substrates. Three examples are described of suicide inactivation through the formation of exceptionally stable free radicals at enzymatic active sites.
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Affiliation(s)
- P A Frey
- Department of Biochemistry, University of Wisconsin-Madison, 1710 University Avenue, Madison, Wisconsin 53705, USA.
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15
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Abstract
The replication checkpoint (or ‘S-M checkpoint’) control prevents progression into mitosis when DNA replication is incomplete. Caffeine has been known for some time to have the capacity to override the S-M checkpoint in animal cells. We show here that caffeine also disrupts the S-M checkpoint in the fission yeast Schizosaccharomyces pombe. By contrast, no comparable effects of caffeine on the S. pombe DNA damage checkpoint were seen. S. pombe cells arrested in early S phase and then exposed to caffeine lost viability rapidly as they attempted to enter mitosis, which was accompanied by tyrosine dephosphorylation of Cdc2. Despite this, the caffeine-induced loss of viability was not blocked in a temperature-sensitive cdc2 mutant incubated at the restrictive temperature, although catastrophic mitosis was prevented under these conditions. This suggests that, in addition to S-M checkpoint control, a caffeine-sensitive function may be important for maintenance of cell viability during S phase arrest. The lethality of a combination of caffeine with the DNA replication inhibitor hydroxyurea was suppressed by overexpression of Cds1 or Chk1, protein kinases previously implicated in S-M checkpoint control and recovery from S phase arrest. In addition, the same combination of drugs was specifically tolerated in cells overexpressing either of two novel S. pombe genes isolated in a cDNA library screen. These findings should allow further molecular investigation of the regulation of S phase arrest, and may provide a useful system with which to identify novel drugs that specifically abrogate the checkpoint control.
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Affiliation(s)
- S W Wang
- Imperial Cancer Research Fund, Cell Regulation Laboratory, PO Box 123, Lincoln's Inn Fields, London WC2 A3P, UK
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16
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Abstract
Two catalytic functions were required, minimally, for the appearance of DNA in evolution: a ribonucleotide reductase (RNR) and a reverse transcriptase (RT). If one accepts the explanatory strength of the RNA world model, it is clear that DNA molecules arose in the RNA world at some stage during the early evolution of cells. I suggest that competition for limited and valuable resources such as nucleotides, amino acids, and sugars made an early appearance among RNA cells, RNA viruses, viroids, and RNA plasmids. Structural and functional similarities between the different types of polymerases favor the simple hypothesis that the first RTs were RNA polymerase mutants that preferentially joined together preexisting deoxyribonucleotide triphosphates (dNTPs) using RNA templates. What was the role of dNTPs inside cells before DNA was synthesized and tested by natural selection? The oxygen atom that is removed by the reductase is of crucial importance to many ribozyme functions, since the 2'-OH is a strong nucleophile that forms transitional states during catalysis. Consequently, a RNR may have been used by cellular parasites to inhibit ribozyme action. Thus, DNA may have been, initially, an inert by-product of retrotranscription in lineages that acquired RTs and could synthesize DNA molecules using cellular RNA templates to detoxify the intracellular environment. DNA was useless as template until a transcriptase (DNA-dependent RNA polymerase) evolved that could copy (-)DNA to reconstitute the (+)RNA genome, indeed a successful way of confronting ribonuclease threats in the RNA world.
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Affiliation(s)
- P E León
- School of Medicine and Cell and Molecular Biology Research Center (CIBCM), Universidad de Costa Rica, San José, Costa Rica.
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Harris P, Kersey PJ, McInerny CJ, Fantes PA. Cell cycle, DNA damage and heat shock regulate suc22+ expression in fission yeast. Mol Gen Genet 1996; 252:284-91. [PMID: 8842148 DOI: 10.1007/bf02173774] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The suc22+ gene of Schizosaccharomyces pombe encodes the small subunit of ribonucleotide reductase. Two transcripts that hybridise to suc22+ have previously been described: a constitutive transcript of 1.5 kb, and a transcript of approximately 1.9 kb that is induced when DNA replication is blocked by hydroxyurea. In this paper we show that both transcripts derive from the suc22+ gene, are polyadenylated, and have transcription initiation sites separated by approximately 550 nucleotides. The absence of translation initiation codons and predicted intron splice sites within this 550 nucleotide region suggests strongly that both transcripts encode the same protein. Under normal growth conditions, the larger suc22+ transcript is present at a very low level. This low level expression is periodic during the cell cycle, showing a pattern similar to that of other genes under regulation by MCB elements with a maximum in G1/S phase. Consistent with this, there are MCB elements upstream of the initiation site of the transcript. This pattern of expression contrasts with the continuous expression, at a much higher level, of the smaller suc22+ transcript. The larger suc22+ transcript is induced by exposure of cells to 4-nitroquinoline oxide (4-NQO),a UV-mimetic agent that causes DNA damage. The transcriptional response to 4-NQO is observed in cells previously arrested in G2 by a cdc2ts mutation, demonstrating that induction can occur outside S phase. We show that the rad1+ gene, part of the mitotic checkpoint, is required for induction of the large transcript. Exposure of cells to heat shock also induces the suc22+ large transcript: a consensus heat shock element has been identified upstream of the large transcript start site.
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Affiliation(s)
- P Harris
- Institute of Cell and Molecular Biology, University of Edinburgh, UK
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18
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Ochiai E. [Free radicals and metalloenzymes]. Seikagaku 1991; 63:1175-84. [PMID: 1663146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- E Ochiai
- Department of Chemistry, Juniata College, Huntingdon, Pa 16652
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Abstract
The enzyme ribonucleotide reductase furnishes precursors for the DNA synthesis of all living cells. One of its constituents, the free radical protein, has an unusual alpha-helical structure. There are two iron centres that are about 25 A apart in the dimeric molecule. Tyrosine 122, which harbours the stable free radical necessary for the activity of ribonucleotide reductase, is buried inside the protein and is located 5 A from the closest iron atom.
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Affiliation(s)
- P Nordlund
- Department of Molecular Biology, Swedish University of Agricultural Sciences, Uppsala
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20
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Abstract
Naturally occurring tyrosine radicals from the M2 subunit of ribonucleotide reductase (RR) have been recorded by ESR in proliferating ordinary Ehrlich-ascites (EA) tumor cells of mice. Tyrosine radicals are stable in EA cells at room temperature for 2 h. Up to 500 mW no microwave saturation occurs. The relatively high stability and non-saturation of tyrosine radicals in EA cells suggests a suitable protein conformation in the M2 subunit enabling a close contact between the tyrosine radical and the antiferromagnetic iron complex. This facilitates an ESR study of functionally essential tyrosine radicals of RR in EA cells at low temperature and recommends this cellular system for studying such processes as inhibition and activation, which change the content of tyrosine radicals of the proliferation-linked RR. Oxygen treatment of non-proliferating (quiescent) EA cells reactivates tyrosine radicals 2-3 fold as found in strongly proliferating cells. We conclude that in quiescent cells, suffering from a lack of oxygen due to their high density in the peritoneal cavity, a reactivation of tyrosine radicals occurs by oxidation of non-radical tyrosine residues of inactive M2 subunits.
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Affiliation(s)
- G Lassmann
- Central Institute of Molecular Biology, Academy of Sciences of GDR, Berlin-Buch
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Sahlin M, Petersson L, Gräslund A, Ehrenberg A, Sjöberg BM, Thelander L. Magnetic interaction between the tyrosyl free radical and the antiferromagnetically coupled iron center in ribonucleotide reductase. Biochemistry 1987; 26:5541-8. [PMID: 2823883 DOI: 10.1021/bi00391a049] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Ribonucleotide reductases from Escherichia coli and from mammalian cells are heterodimeric enzymes. One of the subunits, in the bacterial enzyme protein B2 and in the mammalian enzyme protein M2, contains iron and a tyrosyl free radical that both are essential for enzyme activity. The iron center in protein B2 is an antiferromagnetically coupled pair of high-spin ferric ions. This study concerns magnetic interaction between the tyrosyl radical and the iron center in the two proteins. Studies of the temperature dependence of electron paramagnetic resonance (EPR) relaxation and line shape reveal significant differences between the free radicals in proteins B2 and M2. The observed temperature-dependent enhanced EPR relaxation and line broadening of the enzyme radicals are furthermore completely different from those of a model UV-induced free radical in tyrosine. The results are discussed in terms of magnetic dipolar as well as exchange interactions between the free radical and the iron center in both proteins. The free radical and the iron center are thus close enough in space to exhibit magnetic interaction. For protein M2 the effects are more pronounced than for protein B2, indicating a stronger magnetic interaction.
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Affiliation(s)
- M Sahlin
- Department of Biophysics, Arrhenius Laboratory, University of Stockholm, Sweden
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Bunker G, Petersson L, Sjöberg BM, Sahlin M, Chance M, Chance B, Ehrenberg A. Extended X-ray absorption fine structure studies on the iron-containing subunit of ribonucleotide reductase from Escherichia coli. Biochemistry 1987; 26:4708-16. [PMID: 3311152 DOI: 10.1021/bi00389a017] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Iron K-edge X-ray absorption spectra were obtained on the protein B2, the small subunit of ribonucleotide reductase from Escherichia coli. Protein B2 contains a binuclear iron center with many properties in common with the iron center of oxidized hemerythrins. The extended X-ray absorption fine structure (EXAFS) measurements on protein B2 were analyzed and compared with published data for oxyhemerythrin. In protein B2 there are, in the first coordination shell around each Fe atom, five or six oxygen or nitrogen atoms that are directly coordinated ligands. In oxyhemerythrin there are six ligands to each iron. As in oxyhemerythrin, one of the ligands in the first shell of protein B2 is at a short distance, about 1.78 A, confirming the existence of a mu-oxo bridge. The other atoms of the first shell are at an average distance of 2.04 A, which is about 0.1 A shorter than in oxyhemerythrin. In protein B2 the Fe-Fe distance is in the range 3.26-3.48 A, and the bridging angle falls between 130 and 150 degrees. On the basis of these data, there is no direct evidence for any histidine ligands in protein B2, but the noise level leaves way for the possibility of a maximum of about three histidines for each Fe pair. The X-ray absorption spectrum of a hydroxyurea-treated sample was not significantly different from that of the native protein B2, which implies that no significant alteration in the structure of the iron site occurs upon destruction of the tyrosine radical.
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Affiliation(s)
- G Bunker
- Institute for Structural and Functional Studies, Philadelphia, Pennsylvania 19104
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23
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Sahlin M, Ehrenberg A, Gräslund A, Sjöberg BM. Paramagnetically shifted resonances in 1H NMR spectra of ribonucleotide reductase from Escherichia coli. J Biol Chem 1986; 261:2778-80. [PMID: 3512541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The 400-MHz 1H NMR spectra of the subunit B2 of ribonucleotide reductase from Escherichia coli show paramagnetically shifted resonances at 24 ppm (exchangeable protons) and at 19 ppm (nonexchangeable protons). The protein contains an antiferromagnetically coupled dimeric iron center and a tyrosyl free radical. The paramagnetically shifted resonances must be due to the iron center, since they remain essentially unchanged in protein B2 with and without free radical. In analogy with recently published results for hemerythrin from Phascolopsis gouldii, which has a similar iron center, the 24-ppm resonance is suggested to arise from histidine ligands to the iron ions.
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24
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Sjöberg BM, Loehr TM, Sanders-Loehr J. Raman spectral evidence for a mu-oxo bridge in the binuclear iron center of ribonucleotide reductase. Biochemistry 1982; 21:96-102. [PMID: 7037052 DOI: 10.1021/bi00530a017] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The Raman spectrum of the B2 subunit of Escherichia coli ribonucleotide reductase shows a peak at 496 cm-1 that appears to be in resonance with the 370-nm electronic transition of the binuclear iron center in both the native and radical-free forms of the protein. Exposure of the protein to H218O causes the peak to shift to 481 cm-1, indicating that the vibrational mode is due to an Fe-O moiety in which the oxygen can exchange with solvent. The rate of oxygen exchange (kobsd = 8.3 x 10-4 s-1) is consistent with a mu-oxo-bridged structure. Protonation of the oxygen is unlikely since the Fe-O vibration fails to shift to lower frequency in D2O. Instead, there is a gradual increase in the vibrational frequency with time to a maximum value of 502 cm-1 after 3 h in 70% with time to a maximum value of 602 cm-1 after 3 h in 70% D2O. Apparently, the deuteration of successive protein functional groups causes a slight alteration in the structure of the binuclear iron center. The resonance Raman characteristics of the Fe-O-Fe group in protein B2 are similar to those previously reported for the mu-oxo-bridged binuclear iron center in hemerythrin. A further similarity between the two proteins is the high degree of alpha-helical content. Circular dichroism measurements place this value at approximately 60% for the B2 subunit of ribonucleotide reductase.
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26
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Sjöberg BM, Reichard P, Gräslund A, Ehrenberg A. The tyrosine free radical in ribonucleotide reductase from Escherichia coli. J Biol Chem 1978; 253:6863-5. [PMID: 211133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
One of the two nonidentical subunits of ribonucleotide reductase from Escherichia coli, protein B2, contains an organic free radical required for enzyme activity. Earlier isotope subtitution experiments (Sjöberg, B.-M., Reichard, P. Gräslund, A., and Ehrenberg, A. (1977) J. Biol. Chem. 252, 536-541) demonstrated that the radical was localized to a tyrosine residue of the enzyme and suggested that the spin density of the radical was centered at the methylene carbon of tyrosine. However, additional isotope substitution experiments now show that the spin density of the radical must be delocalized over the aromatic ring of the tyrosine residue.
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Schrauzer GN. New developments in the field of vitamin B12: enzymatic reactions dependent upon corrins and coenzyme B12. Angew Chem Int Ed Engl 1977; 16:233-44. [PMID: 404942 DOI: 10.1002/anie.197702331] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Buettner GR, Coffman RE. EPR determination of the Co(II)-free radical magnetic geometry of the "doublet" species arising in a coenzyme B-12-enzyme reaction. Biochim Biophys Acta 1977; 480:495-505. [PMID: 189818 DOI: 10.1016/0005-2744(77)90042-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The physical significance of the observed structure of the EPR signal, commonly known as the "doublet" spectrum, is that it contains information not only about the exchange coupling but also about the geometry of the magnetic dipole-dipole spin-spin coupling. We can show this because we have developed a general method of analysis applicable to this type of system and because we demand a quantitative fit of theory to experiment at two microwave frequencies. We have chosen the "doublet" free radical signal, which arises in the ribonucleotide reductase-5'-deoxyadenosylcobalamin system (from Lactobacillus leichmannii, see Hamilton et al., Biochemistry 11, 4696--4705 (1972)), for study, for the particular reason that the 35 GHz "doublet" spectrum has three components (in this case) rather than two, which provides an important test of the recently proposed model of isotropic exchange coupling by Schepler et al. ((1975) Biochim. Biophys. Acta 397, 510--518). We find that a quantitative fit to the EPR "doublet" lineshape can be obtained with a model of isotropic exchange, and a "point" magnetic dipole-dipole interaction acting over a distance of 9.9 A with the radical located approx. 34 degrees off the principal gzz axis and less than 1 degree off the principal gxx axis of the Co(II) in the corrin ring. Quantitative fits of the doublet portion of the observed lineshape at both 9 and 35 GHz were achieved with this model, assuming an axially symmetric free radical signal and a Gaussian spin-packet lineshape with isotropic linewidth.
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