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  • 1.
    Loderer, Christoph
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Jonna, Venkateswara Rao
    Crona, Mikael
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Rozman Grinberg, Inna
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sahlin, Margareta
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Hofer, Anders
    Lundin, Daniel
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sjöberg, Britt-Marie
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    A unique cysteine-rich zinc finger domain present in a majority of class II ribonucleotide reductases mediates catalytic turnover2017In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 292, no 46, p. 19044-19054Article in journal (Refereed)
    Abstract [en]

    Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides to the corresponding deoxyribonucleotides, used in DNA synthesis and repair. Two different mechanisms help deliver the required electrons to the RNR active site. Formate can be used as reductant directly in the active site, or glutaredoxins or thioredoxins reduce a C-terminal cysteine pair, which then delivers the electrons to the active site. Here, we characterized a novel cysteine-rich C-terminal domain (CRD), which is present in most class II RNRs found in microbes. The NrdJd-type RNR from the bacterium Stackebrandtia nassauensis was used as a model enzyme. We show that the CRD is involved in both higher oligomeric state formation and electron transfer to the active site. The CRD-dependent formation of high oligomers, such as tetramers and hexamers, was induced by addition of dATP or dGTP, but not of dTTP or dCTP. The electron transfer was mediated by an array of six cysteine residues at the very C-terminal end, which also coordinated a zinc atom. The electron transfer can also occur between subunits, depending on the enzyme's oligomeric state. An investigation of the native reductant of the system revealed no interaction with glutaredoxins or thioredoxins, indicating that this class II RNR uses a different electron source. Our results indicate that the CRD has a crucial role in catalytic turnover and a potentially new terminal reduction mechanism and suggest that the CRD is important for the activities of many class II RNRs.

  • 2.
    Rozman Grinberg, Inna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Berglund, Sigrid
    Hasan, Mahmudul
    Lundin, Daniel
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Ho, Felix M.
    Magnuson, Ann
    Logan, Derek T.
    Sjöberg, Britt-Marie
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Berggren, Gustav
    Class Id ribonucleotide reductase utilizes a Mn-2(IV,III) cofactor and undergoes large conformational changes on metal loading2019In: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 24, no 6, p. 863-877Article in journal (Refereed)
    Abstract [en]

    Outside of the photosynthetic machinery, high-valent manganese cofactors are rare in biology. It was proposed that a recently discovered subclass of ribonucleotide reductase (RNR), class Id, is dependent on a Mn-2(IV,III) cofactor for catalysis. Class I RNRs consist of a substrate-binding component (NrdA) and a metal-containing radical-generating component (NrdB). Herein we utilize a combination of EPR spectroscopy and enzyme assays to underscore the enzymatic relevance of the Mn-2(IV,III) cofactor in class Id NrdB from Facklamia ignava. Once formed, the Mn-2(IV,III) cofactor confers enzyme activity that correlates well with cofactor quantity. Moreover, we present the X-ray structure of the apo- and aerobically Mn-loaded forms of the homologous class Id NrdB from Leeuwenhoekiella blandensis, revealing a dimanganese centre typical of the subclass, with a tyrosine residue maintained at distance from the metal centre and a lysine residue projected towards the metals. Structural comparison of the apo- and metal-loaded forms of the protein reveals a refolding of the loop containing the conserved lysine and an unusual shift in the orientation of helices within a monomer, leading to the opening of a channel towards the metal site. Such major conformational changes have not been observed in NrdB proteins before. Finally, in vitro reconstitution experiments reveal that the high-valent manganese cofactor is not formed spontaneously from oxygen, but can be generated from at least two different reduced oxygen species, i.e. H2O2 and superoxide (O2 center dot-). Considering the observed differences in the efficiency of these two activating reagents, we propose that the physiologically relevant mechanism involves superoxide.

  • 3.
    Rozman Grinberg, Inna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lundin, Daniel
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Hasan, Mahmudul
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Lund University, Sweden.
    Crona, Mikael
    Jonna, Venkateswara Rao
    Loderer, Chrishtoph
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sahlin, Margareta
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Markova, Natalia
    Borovok, Ilya
    Berggren, Gustav
    Hofer, Anders
    Logan, Derek T.
    Sjöberg, Britt-Marie
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Novel ATP-cone-driven allosteric regulation of ribonucleotide reductase via the radical-generating subunit2018In: eLIFE, E-ISSN 2050-084X, Vol. 7, article id e31529Article in journal (Refereed)
    Abstract [en]

    Ribonucleotide reductases (RNRs) are key enzymes in DNA metabolism, with allosteric mechanisms controlling substrate specificity and overall activity. In RNRs, the activity master-switch, the ATP-cone, has been found exclusively in the catalytic subunit. In two class I RNR subclasses whose catalytic subunit lacks the ATP-cone, we discovered ATP-cones in the radical-generating subunit. The ATP-cone in the Leeuwenhoekiella blandensis radical-generating subunit regulates activity via quaternary structure induced by binding of nucleotides. ATP induces enzymatically competent dimers, whereas dATP induces non-productive tetramers, resulting in different holoenzymes. The tetramer forms by interactions between ATP-cones, shown by a 2.45 A crystal structure. We also present evidence for an (MnMnIV)-Mn-III metal center. In summary, lack of an ATP-cone domain in the catalytic subunit was compensated by transfer of the domain to the radical-generating subunit. To our knowledge, this represents the first observation of transfer of an allosteric domain between components of the same enzyme complex.

  • 4.
    Rozman Grinberg, Inna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lundin, Daniel
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Sahlin, Margareta
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Crona, Mikael
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Swedish Orphan Biovitrum AB, Sweden.
    Berggren, Gustav
    Hofer, Anders
    Sjöberg, Britt-Marie
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    A glutaredoxin domain fused to the radical-generating subunit of ribonucleotide reductase (RNR) functions as an efficient RNR reductant2018In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 293, no 41, p. 15889-15900Article in journal (Refereed)
    Abstract [en]

    Class I ribonucleotide reductase (RNR) consists of a catalytic subunit (NrdA) and a radical-generating subunit (NrdB) that together catalyze reduction of ribonucleotides to their corresponding deoxyribonucleotides. NrdB from the firmicute Facklamia ignava is a unique fusion protein with N-terminal addons of a glutaredoxin (Grx) domain followed by an ATP-binding domain, the ATP cone. Grx, usually encoded separately from the RNR operon, is a known RNR reductant. We show that the fused Grx domain functions as an efficient reductant of the F. ignava class I RNR via the common dithiol mechanism and, interestingly, also via a monothiol mechanism, although less efficiently. To our knowledge, a Grx that uses both of these two reaction mechanisms has not previously been observed with a native substrate. The ATP cone is in most RNRs an N-terminal domain of the catalytic subunit. It is an allosteric on/off switch promoting ribonucleotide reduction in the presence of ATP and inhibiting RNR activity in the presence of dATP. We found that dATP bound to the ATP cone of F. ignava NrdB promotes formation of tetramers that cannot form active complexes with NrdA. The ATP cone bound two dATP molecules but only one ATP molecule. F. ignava NrdB contains the recently identified radical-generating cofactor Mn-III/Mn-IV. We show that NrdA from F. ignava can form a catalytically competent RNR with the Mn-III/Mn-IV-containing NrdB from the flavobacterium Leeuwenhoekiella blandensis. In conclusion, F. ignava NrdB is fused with a Grx functioning as an RNR reductant and an ATP cone serving as an on/off switch.

  • 5.
    Rozman Grinberg, Inna
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Tel Aviv University, Israel.
    Yaniv, Oren
    Ortiz de Ora, Lizett
    Muñoz-Gutiérrez, Iván
    Hershko, Almog
    Livnah, Oded
    Bayer, Edward A.
    Borovok, Ilya
    Frolow, Felix
    Lamed, Raphael
    Voronov-Goldman, Milana
    Distinctive ligand-binding specificities of tandem PA14 biomass-sensory elements from Clostridium thermocellum and Clostridium clariflavum2019In: Proteins: Structure, Function, and Bioinformatics, ISSN 0887-3585, E-ISSN 1097-0134, Vol. 87, no 11, p. 917-930Article in journal (Refereed)
    Abstract [en]

    Cellulolytic clostridia use a highly efficient cellulosome system to degrade polysaccharides. To regulate genes encoding enzymes of the multi-enzyme cellulosome complex, certain clostridia contain alternative sigma I (sigma(I)) factors that have cognate membrane-associated anti-sigma(I) factors (RsgIs) which act as polysaccharide sensors. In this work, we analyzed the structure-function relationship of the extracellular sensory elements of Clostridium (Ruminiclostridium) thermocellum and Clostridium clariflavum (RsgI3 and RsgI4, respectively). These elements were selected for comparison, as each comprised two tandem PA14-superfamily motifs. The X-ray structures of the PA14 modular dyads from the two bacterial species were determined, both of which showed a high degree of structural and sequence similarity, although their binding preferences differed. Bioinformatic approaches indicated that the DNA sequence of promoter of sigI/rsgI operons represents a strong signature, which helps to differentiate binding specificity of the structurally similar modules. The sigma(I4)-dependent C. clariflavum promoter sequence correlates with binding of RsgI4_PA14 to xylan and was identified in genes encoding xylanases, whereas the sigma(I3)-dependent C. thermocellum promoter sequence correlates with RsgI3_PA14 binding to pectin and regulates pectin degradation-related genes. Structural similarity between clostridial PA14 dyads to PA14-containing proteins in yeast helped identify another crucial signature element: the calcium-binding loop 2 (CBL2), which governs binding specificity. Variations in the five amino acids that constitute this loop distinguish the pectin vs xylan specificities. We propose that the first module (PA14(A)) is dominant in directing the binding to the ligand in both bacteria. The two X-ray structures of the different PA14 dyads represent the first reported structures of tandem PA14 modules.

1 - 5 of 5
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