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  • 1.
    Crona, Mikael
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Quaternary structure and interaction approaches to allosteric regulation of class I ribonucleotide reductases2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Deoxyribonucleic acid (DNA) chains in which our genetic blueprint is stored are built from four DNA precursors by DNA polymerases. The enzyme ribonucleotide reductase (RNR) provides the only de novo synthesis pathway of deoxyribonucleotides from ribonucleotides and is essential for nearly all organisms. All four ribonucleotides are substrates for RNR and key to this flexibility is a sophisticated allosteric regulation. Nucleotide effectors (ATP, dATP, dTTP or dGTP) binding to the allosteric specificity site determines substrate specificity for the active site. When present at high concentrations, dATP binds to the allosteric overall activity site and inhibits activity by an unknown mechanism. Three approaches, RNR activity measurements, subunit interaction studies and quaternary structure studies were applied to four different class I RNRs to address the allosteric overall regulation. We found that allosteric overall inhibition was closely linked to formation of tight and large RNR protein complexes; α4β4 complex for the Escherichia coli class Ia RNR and α6β2 for the Dictyostelium discoideum class Ia RNR with functional allosteric inhibitions. The Aeh1 phage class Ia RNR with a non-functional dATP inhibition showed weak remnant inhibition features, while the Bacillus anthracis class Ib RNR without the allosteric overall regulation domain lacked these features. In addition, we presented the first biochemical characterization of a mechanism to restore protein function after gene fragmentation, we showed that the B. anthracis class Ib RNR was most active when reconstituted with manganese and in the presence of a physiological redoxin protein and we found that the class Ia RNR is the principal RNR in D. discoideum, although the coexisting class II RNR could partly compensate class I RNR inhibition during axenic growth. Finally, our improved method for studying RNR interactions has potential for RNR inhibitor screening.

  • 2.
    Crona, Mikael
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Avesson, Lotta
    Department of Molecular Biology, Swedish University of Agricultural Sciences (SLU), Uppsala .
    Sahlin, Margareta
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Hinas, Andrea
    Department of Molecular Biology, Swedish University of Agricultural Sciences (SLU), Uppsala .
    Klose, Ralph
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Söderbom, Fredrik
    Department of Molecular Biology, Swedish University of Agricultural Sciences (SLU), Uppsala .
    Sjöberg, Britt-Marie
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    The two classes of ribonucleotide reductase in the social amoeba Dictystelium discoideumManuscript (preprint) (Other academic)
  • 3.
    Crona, Mikael
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Furrer, Ernst
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Torrents, Eduard
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Edgell, David R.
    Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario,.
    Sjöberg, Britt-Marie
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Subunit and small-molecule interaction of ribonucleotide reductases via surface plasmon resonance biosensor analyses2010In: Protein Engineering Design & Selection, ISSN 1741-0126, E-ISSN 1741-0134, Vol. 23, no 8, p. 633-641Article in journal (Refereed)
    Abstract [en]

    Ribonucleotide reductase (RNR) synthesizes deoxyribonucleotides for DNA replication and repair and is controlled by sophisticated allosteric regulation involving differential affinity of nucleotides for regulatory sites. We have developed a robust and sensitive method for coupling biotinylated RNRs to surface plasmon resonance streptavidin biosensor chips via a 30.5 Å linker. In comprehensive studies on three RNRs effector nucleotides strengthened holoenzyme interactions, whereas substrate had no effect on subunit interactions. The RNRs differed in their response to the negative allosteric effector dATP that binds to an ATP-cone domain. A tight RNR complex was formed in Escherichia coli class Ia RNR with a functional ATP cone. No strengthening of subunit interactions was observed in the class Ib RNR from the human pathogen Bacillus anthracis that lacks the ATP cone. A moderate strengthening was seen in the atypical Aeromonas hydrophila phage 1 class Ia RNR that has a split catalytic subunit and a non-functional ATP cone with remnant dATP-mediated regulatory features. We also successfully immobilized a functional catalytic NrdA subunit of the E.coli enzyme, facilitating study of nucleotide interactions. Our surface plasmon resonance methodology has the potential to provide biological insight into nucleotide-mediated regulation of any RNR, and can be used for high-throughput screening of potential RNR inhibitors

  • 4.
    Crona, Mikael
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Sjöberg, Britt-Marie
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Moffatt, Connor
    Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario.
    Edgell, David R.
    Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario.
    Friedrich, Nancy C.
    Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario.
    Hofer, Anders
    Department of Medical Biochemistry and Biophysics, Umeå University.
    Assembly of a fragmented ribonucleotide reductase by protein interaction domains derived from a mobile genetic element2011In: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 39, no 4, p. 1381-1389Article in journal (Refereed)
    Abstract [en]

    Ribonucleotide reductase (RNR) is a critical enzyme of nucleotide metabolism, synthesizing precursors for DNA replication and repair. In prokaryotic genomes, RNR genes are commonly targeted by mobile genetic elements, including free standing and intron-encoded homing endonucleases and inteins. Here, we describe a unique molecular solution to assemble a functional product from the RNR large subunit gene, nrdA that has been fragmented into two smaller genes by the insertion of mobE, a mobile endonuclease. We show that unique sequences that originated during the mobE insertion and that are present as C- and N-terminal tails on the split NrdA-a and NrdA-b polypeptides, are absolutely essential for enzymatic activity. Our data are consistent with the tails functioning as protein interaction domains to assemble the tetrameric (NrdA-a/NrdA-b)2 large subunit necessary for a functional RNR holoenzyme. The tails represent a solution distinct from RNA and protein splicing or programmed DNA rearrangements to restore function from a fragmented coding region and may represent a general mechanism to neutralize fragmentation of essential genes by mobile genetic elements.

  • 5.
    Crona, Mikael
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Torrents, Eduard
    Cellular Biotechnology, Institute for Bioengineering of Catalonia, Barcelona, Spain.
    Hofer, Anders
    Department of Medical Biochemistry & Biophysics, Umeå University.
    Furrer, Ernst
    Tomter, Ane
    Department of Molecular Biosciences, University of Oslo, Norway.
    Rohr, Åsmund
    Andersson, Kristoffer
    Sahlin, Margareta
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Sjöberg, Britt-Marie
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    NrdH-redoxin mediates high enzyme activity in manganese-reconstituted ribonucleotide reductase from Bacillus anthracisManuscript (preprint) (Other academic)
1 - 5 of 5
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