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| 2. |
- Clausen, Anders Ranegaard, et al.
(författare)
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Thymidine kinases in archaea
- 2006
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Ingår i: Nucleosides, Nucleotides & Nucleic Acids. - : Informa UK Limited. - 1525-7770 .- 1532-2335. ; 25:9-11, s. 1159-1163
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Tidskriftsartikel (refereegranskat)abstract
- Twenty-six fully sequenced archaeal genomes were searched for genes coding for putative deoxyribonucleoside kinases (dNKs). We identified only 5 human-like thymidine kinase 1 genes (TK1s) and none for non-TK1 kinases. Four TK1s were identified in the Euryarchaea and one was found in the Crenarchaea, while none was found in Nanoarchaeum. The identified TK1s have high identity to Gram-positive bacteria TK1s. The TK1s from archaea, Gram-positive bacteria and eukaryotes share the same common ancestor, while the TK1s from Gram-negative bacteria belong to a less-related subgroup. It seems that a functional deoxyribonucleoside salvage pathway is not crucial for the archaeal cell.
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| 3. |
- Clausen, Anders Ranegaard, et al.
(författare)
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Two thymidine kinases and one multisubstrate deoxyribonucleoside kinase salvage DNA precursors in Arabidopsis thaliana.
- 2012
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X. ; 279:20, s. 3889-3897
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Tidskriftsartikel (refereegranskat)abstract
- Deoxyribonucleotides are the building blocks of DNA and can be synthesized via de novo and salvage pathways. Deoxyribonucleoside kinases (dNKs) salvage deoxyribonucleosides by transfer of a phosphate group to the 5' of a deoxyribonucleoside. This salvage pathway is well characterized in mammals but in contrast little is known about how plants salvage deoxyribonucleosides. We show that during salvage, deoxyribonucleosides can be phosphorylated by extracts of Arabidopsis thaliana into corresponding mono-phosphate compounds with a surprising preference for purines over pyrimidines. Deoxyribonucleoside kinase activities were present in all tissues during all growth stages. In the A. thaliana genome we identified two types of genes that could encode enzymes which are involved in the salvage of deoxyribonucleosides. Thymidine kinase activity was encoded by two thymidine kinase 1-like genes (AtTK1a and AtTK1b) and deoxyadenosine, deoxyguanosine and deoxycytidine kinase activities were encoded by a single AtdNK gene. T-DNA insertion lines of AtTK1a and AtTK1b mutant genes had normal growth, but AtTK1a AtTK1b double mutants died at an early stage, which indicates that AtTK1a and AtTK1b catalyze redundant reactions. Our results point out a crucial role for salvage of thymidine during early plant development. © 2012 The Authors Journal compilation © 2012 FEBS.
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| 4. |
- Knecht, W., et al.
(författare)
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Drosophila deoxyribonucleoside kinase mutants with enhanced ability to phosphorylate purine analogs
- 2007
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Ingår i: Gene Therapy. - : Springer Science and Business Media LLC. - 0969-7128 .- 1476-5462. ; 14:17, s. 1278-1286
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Tidskriftsartikel (refereegranskat)abstract
- Transduced deoxyribonucleoside kinases (dNK) can be used to kill recipient cells in combination with nucleoside prodrugs. The Drosophila melanogaster multisubstrate dNK (Dm-dNK) displays a superior turnover rate and has a great plasticity regarding its substrates. We used directed evolution to create Dm-dNK mutants with increased specificity for several nucleoside analogs (NAs) used as anticancer or antiviral drugs. Four mutants were characterized for the ability to sensitize Escherichia coli toward analogs and for their substrate specificity and kinetic parameters. The mutants had a reduced ability to phosphorylate pyrimidines, while the ability to phosphorylate purine analogs was relatively similar to the wild-type enzyme. We selected two mutants, for expression in the osteosarcoma 143B, the glioblastoma U-87M-G and the breast cancer MCF7 cell lines. The sensitivities of the transduced cell lines in the presence of the NAs fludarabine (F-AraA), cladribine (CdA), vidarabine and cytarabine were compared to the parental cell lines. The sensitivity of 143B cells was increased by 470-fold in the presence of CdA and of U-87M-G cells by 435fold in the presence of F-AraA. We also show that a choice of the selection and screening system plays a crucial role when optimizing suicide genes by directed evolution.
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| 5. |
- Kosinska, Urszula, et al.
(författare)
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Structural studies of thymidine kinases from Bacillus anthracis and Bacillus cereus provide insights into quaternary structure and conformational changes upon substrate binding
- 2007
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X. ; 274:3, s. 727-737
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Tidskriftsartikel (refereegranskat)abstract
- Thymidine kinase (TK) is the key enzyme in salvaging thymidine to produce thymidine monophosphate. Owing to its ability to phosphorylate nucleoside analogue prodrugs, TK has gained attention as a rate-limiting drug activator. We describe the structures of two bacterial TKs, one from the pathogen Bacillus anthracis in complex with the substrate dT, and the second from the food-poison-associated Bacillus cereus in complex with the feedback inhibitor dTTP. Interestingly, in contrast with previous structures of TK in complex with dTTP, in this study dTTP occupies the phosphate donor site and not the phosphate acceptor site. This results in several conformational changes compared with TK structures described previously. One of the differences is the way tetramers are formed. Unlike B. anthracis TK, B. cereus TK shows a loose tetramer. Moreover, the lasso-domain is in open conformation in B. cereus TK without any substrate in the active site, whereas in B. anthracis TK the loop conformation is closed and thymidine occupies the active site. Another conformational difference lies within a region of 20 residues that we refer to as phosphate-binding beta-hairpin. The phosphate-binding beta-hairpin seems to be a flexible region of the enzyme which becomes ordered upon formation of hydrogen bonds to the alpha-phosphate of the phosphate donor, dTTP. In addition to descriptions of the different conformations that TK may adopt during the course of reaction, the oligomeric state of the enzyme is investigated.
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| 6. |
- Sandrini, Michael, et al.
(författare)
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Deoxyribonucleoside kinases activate nucleoside antibiotics in severe pathogenic bacteria.
- 2007
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Ingår i: Antimicrobial Agents and Chemotherapy. - 1098-6596. ; 51:8, s. 2726-2732
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Tidskriftsartikel (refereegranskat)abstract
- Common bacterial pathogens are becoming progressively more resistant to traditional antibiotics, representing a major public-health crisis. Therefore, there is a need for a variety of antibiotics with alternative modes of action. In our study, several nucleoside analogs were tested against pathogenic staphylococci and streptococci. We show that pyrimidine-based nucleoside analogs, like 3'-azido-3'-deoxythymidine (AZT) and 2',2'-difluoro-2'deoxycytidine (gemcitabine), are specifically activated by the endogenous bacterial deoxyribonucleoside kinases, leading to cell death. Deoxyribonucleoside kinase-deficient Escherichia coli strains become highly susceptible to nucleoside analogs when they express recombinant kinases from Staphylococcus aureus or Streptococcus pyogenes. We further demonstrate that recombinant S. aureus deoxyadenosine kinase efficiently phosphorylates the anticancer drug gemcitabine in vitro and is therefore the key enzyme in the activation pathway. When adult mice were infected intraperitoneally with a fatal dose of S. pyogenes strain AP1 and afterwards received gemcitabine, they failed to develop a systemic infection. Nucleoside analogs may therefore represent a promising alternative for combating pathogenic bacteria.
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| 7. |
- Sandrini, Michael, et al.
(författare)
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Deoxyribonucleoside kinases: two enzyme families catalyze the same reaction
- 2005
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Ingår i: Trends in Biochemical Sciences. - : Elsevier BV. - 0167-7640 .- 0968-0004. ; 30:5, s. 225-228
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Tidskriftsartikel (refereegranskat)abstract
- Mammals have four deoxyribonucleoside kinases, the cytoplasmic (TK1) and mitochondrial (TK2) thymidine kinases, and the deoxycytidine (dCK) and deoxyguanosine (dGK) kinases, which salvage the precursors for nucleic acids synthesis. In addition to the native deoxyribonucleoside substrates, the kinases can phosphorylate and thereby activate a variety of anti-cancer and antiviral prodrugs. Recently, the crystal structure of human TK1 has been solved and has revealed that enzymes with fundamentally different origins and folds catalyze similar, crucial cellular reactions.
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| 8. |
- Sandrini, Michael, et al.
(författare)
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Dictyostelium discoideum salvages purine deoxyribonucleosides by highly specific bacterial-like deoxyribonucleoside kinases
- 2007
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 1089-8638 .- 0022-2836. ; 369:3, s. 653-664
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Tidskriftsartikel (refereegranskat)abstract
- The salvage of deoxyribonucleosides in the social amoeba Dictyostelium discoideum, which has an extremely A + T-rich genome, was investigated. All native deoxyribonucleosides were phosphorylated by D. discoideum cell extracts and we subcloned three deoxyribonucleoside kinase (dNK) encoding genes. D. discoideum thymidine kinase was similar to the human thymidine kinase 1 and was specific for thymidine with a k(m) of 5.1 mu M. The other two cloned kinases were phylogenetically closer to bacterial deoxyribonucleoside kinases than to the eukaryotic enzymes. D. discoideum deoxyadenosine kinase (DddAK) had a K-m for deoxyadenosine of 22.7 mu M and a k(cat) of 3.7 s(-1) and could not efficiently phosphorylate any other native deoxyribonucleoside. D. discoideum deoxyguanosine kinase was also a purine-specific kinase and phosphorylated significantly only deoxyguanosine, with a K-m of 1.4 mu M and a k(cat) of 3 s(-1). The two purine-specific deoxyribonucleoside kinases could represent ancient enzymes present in the common ancestor of bacteria and eukaryotes but remaining only in a few eukaryote lineages. The narrow substrate specificity of the D. discoideum dNKs reflects the biased genome composition and we attempted to explain the strict preference of DddAK for deoxyadenosine by modeling the active center with different substrates. Apart from its native substrate, deoxyadenosine, DddAK efficiently phosphorylated fludarabine. Hence, DddAK could be used in the enzymatic production of fludarabine monophosphate, a drug used in the treatment of chronic lymphocytic leukemia.
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| 9. |
- Sandrini, Michael P. B., et al.
(författare)
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Nucleoside analogues are activated by bacterial deoxyribonucleoside kinases in a species-specific manner
- 2007
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Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 1460-2091 .- 0305-7453. ; 60:3, s. 510-520
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To investigate the bactericidal activity of antiviral and anticancer nucleoside analogues against a variety of pathogenic bacteria and characterize the activating enzymes, deoxyribonucleoside kinases (dNKs). Methods: Several FDA-approved nucleoside analogue drugs were screened for their potential bactericidal activity against several clinical bacterial isolates and type strains. We identified and subcloned the genes coding for putative deoxyribonucleoside kinases in Escherichia coli, Pasteurella multocida, Salmonella enterica, Yersinia enterocolitica, Bacillus cereus, Clostridium perfringens and Listeria monocytogenes. These genes were tested for their ability to increase the susceptibility of a dNK-deficient E. coli strain to various analogues. We overexpressed, purified and characterized the substrate specificity and kinetic properties of the recombinant enzymes from S. enterica and B. cereus. Results: The tested Gram-negative bacteria were susceptible to 3 '-azido-3 '-deoxythymidine (AZT) in the concentration range 0.032-31.6 mu M except for a single E. coli isolate and two Pseudomonas aeruginosa isolates which were resistant to the tested AZT concentrations. Purified recombinant S. enterica thymidine kinase phosphorylated AZT efficiently with a K-m of 73.3 mM and k(cat)/K-m of 6.6 x 10(4) s(-1)M(-1) and is the activator of this drug in vivo. 2 ',2 '-Difluoro-2 '-deoxycytidine ( gemcitabine) was a potent antibiotic against Gram-positive bacteria in the concentration range between 0.001 and 1.0 mu M. The B. cereus deoxyadenosine kinase had a Km for gemcitabine of 33.5 mM and kcat/Km of 5.1 x 10(3) s(-1) M-1 and activates gemcitabine in vivo. S. enterica and B. cereus are now amongst the first bacteria with a completely characterized set of dNK enzymes. Conclusions: Bacterial dNKs efficiently activate nucleoside analogues in a species-specific manner. Therefore, nucleoside analogues have a potential to be employed as antibiotics in the fight against emerging multiresistant bacteria.
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| 10. |
- Sandrini, Michael, et al.
(författare)
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Thymidine kinase diversity in bacteria
- 2006
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Ingår i: Nucleosides, Nucleotides & Nucleic Acids. - : Informa UK Limited. - 1525-7770 .- 1532-2335. ; 25:9-11, s. 1153-1158
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Tidskriftsartikel (refereegranskat)abstract
- Thymidine kinases (TKs) appear to be almost ubiquitous and are found in nearly all prokaryotes, eukaryotes, and several viruses. They are the key enzymes in thymidine salvage and activation of several anti-cancer and antiviral drugs. We show that bacterial TKs can be subdivided into 2 groups. The TKs from Gram-positive bacteria are more closely related to the eukaryotic TK1 enzymes than are TKs from Gram-negative bacteria.
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