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1.
DNA Repair (Amst) ; 78: 45-59, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30959406

RESUMO

Endonuclease III (EndoIII) is a bifunctional DNA glycosylase that removes oxidized pyrimidines from DNA. The genome of Deinococcus radiodurans encodes for an unusually high number of DNA glycosylases, including three EndoIII enzymes (drEndoIII1-3). Here, we compare the properties of these enzymes to those of their well-studied homologues from E. coli and human. Our biochemical and mutational data, reinforced by MD simulations of EndoIII-DNA complexes, reveal that drEndoIII2 exhibits a broad substrate specificity and a catalytic efficiency surpassing that of its counterparts. In contrast, drEndoIII1 has much weaker and uncoupled DNA glycosylase and AP-lyase activities, a characteristic feature of eukaryotic DNA glycosylases, and was found to present a relatively robust activity on single-stranded DNA substrates. To our knowledge, this is the first report of such an activity for an EndoIII. In the case of drEndoIII3, no catalytic activity could be detected, but its ability to specifically recognize lesion-containing DNA using a largely rearranged substrate binding pocket suggests that it may play an alternative role in genome maintenance. Overall, these findings reveal that D. radiodurans possesses a unique set of DNA repair enzymes, including three non-redundant EndoIII variants with distinct properties and complementary activities, which together contribute to genome maintenance in this bacterium.


Assuntos
Reparo do DNA , DNA Complementar/genética , Deinococcus/enzimologia , Deinococcus/genética , Desoxirribonuclease (Dímero de Pirimidina)/genética , Desoxirribonuclease (Dímero de Pirimidina)/metabolismo , Mutação , Biocatálise , DNA Complementar/metabolismo , Desoxirribonuclease (Dímero de Pirimidina)/química , Humanos , Simulação de Dinâmica Molecular , Conformação Proteica , Pirimidinas/metabolismo , Especificidade por Substrato
2.
J Struct Biol ; 191(2): 87-99, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26172070

RESUMO

While most bacteria possess a single gene encoding the bifunctional DNA glycosylase Endonuclease III (EndoIII) in their genomes, Deinococcus radiodurans possesses three: DR2438 (DrEndoIII1), DR0289 (DrEndoIII2) and DR0982 (DrEndoIII3). Here we have determined the crystal structures of DrEndoIII1 and an N-terminally truncated form of DrEndoIII3 (DrEndoIII3Δ76). We have also generated a homology model of DrEndoIII2 and measured activity of the three enzymes. All three structures consist of two all α-helical domains, one of which exhibits a [4Fe-4S] cluster and the other a HhH-motif, separated by a DNA binding cleft, similar to previously determined structures of endonuclease III from Escherichia coli and Geobacillus stearothermophilus. However, both DrEndoIII1 and DrEndoIII3 possess an extended HhH motif with extra helical features and an altered electrostatic surface potential. In addition, the DNA binding cleft of DrEndoIII3 seems to be less accessible for DNA interactions, while in DrEndoIII1 it seems to be more open. Analysis of the enzyme activities shows that DrEndoIII2 is most similar to the previously studied enzymes, while DrEndoIII1 seems to be more distant with a weaker activity towards substrate DNA containing either thymine glycol or an abasic site. DrEndoIII3 is the most distantly related enzyme and displays no detectable activity towards these substrates even though the suggested catalytic residues are conserved. Based on a comparative structural analysis, we suggest that the altered surface potential, shape of the substrate-binding pockets and specific amino acid substitutions close to the active site and in the DNA interacting loops may underlie the unexpected differences in activity.


Assuntos
Proteínas de Bactérias/química , Deinococcus/enzimologia , Desoxirribonuclease (Dímero de Pirimidina)/química , Motivos de Aminoácidos , Sequência de Aminoácidos , Proteínas de Bactérias/fisiologia , Clonagem Molecular , Cristalografia por Raios X , Modelos Moleculares , Dados de Sequência Molecular , Estrutura Terciária de Proteína , Alinhamento de Sequência , Análise de Sequência de Proteína , Relação Estrutura-Atividade
3.
Acta Crystallogr F Struct Biol Commun ; 70(Pt 12): 1688-92, 2014 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-25484227

RESUMO

Endonuclease III is a bifunctional DNA glycosylase that removes a wide range of oxidized bases in DNA. Deinococcus radiodurans is an extreme radiation-resistant and desiccation-resistant bacterium and possesses three genes encoding endonuclease III enzymes in its genome: DR2438 (EndoIII-1), DR0289 (EndoIII-2) and DR0982 (EndoIII-3). Here, EndoIII-1 and an N-terminally truncated form of EndoIII-3 (EndoIII-3Δ76) have been expressed, purified and crystallized, and preliminary X-ray crystallographic analyses have been performed to 2.15 and 1.31 Šresolution, respectively. The EndoIII-1 crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 181.38, b = 38.56, c = 37.09 Å, ß = 89.34° and one molecule per asymmetric unit. The EndoIII-3Δ76 crystals also belonged to the monoclinic space group C2, but with unit-cell parameters a = 91.47, b = 40.53, c = 72.47 Å, ß = 102.53° and one molecule per asymmetric unit. The EndoIII-1 structure was determined by molecular replacement, while the truncated EndoIII-3Δ76 structure was determined by single-wavelength anomalous dispersion phasing. Refinement of the structures is in progress.


Assuntos
Deinococcus/enzimologia , Endonucleases/metabolismo , Cristalização , Cristalografia por Raios X , Endonucleases/química
4.
J Biol Chem ; 280(12): 11152-64, 2005 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-15657030

RESUMO

Homo- and heterodimerization of the opioid receptors with functional consequences were reported previously. However, the exact nature of these putative dimers has not been identified. In current studies, the nature of the heterodimers was investigated by producing the phenotypes of the 1:1 heterodimers formed between the constitutively expressed mu-opioid receptor (MOR) and the ponasterone A-induced expression of delta-opioid receptor (DOR) in EcR293 cells. By examining the trafficking of the cell surface-located MOR and DOR, we determined that these two receptors endocytosed independently. Using cell surface expression-deficient mutants of MOR and DOR, we observed that the corresponding wild types of these receptors could not rescue the cell surface expression of the mutants, whereas the antagonist naloxone could. Furthermore, studies with constitutive or agonist-induced receptor internalization also indicated that MOR and DOR endocytosed independently and could not "drag in" the corresponding wild types or endocytosis-deficient mutants. Additionally, the heterodimer phenotypes could be eliminated by the pretreatment of the EcR293 cells with pertussis toxin and could be modulated by the deletion of the RRITR sequence in the third intracellular loop that is involved in the receptor-G protein interaction and activation. These data suggest that MOR and DOR heterodimerize only at the cell surface and that the oligomers of opioid receptors and heterotrimeric G protein are the bases for the observed MOR-DOR heterodimer phenotypes.


Assuntos
Proteínas Heterotriméricas de Ligação ao GTP/fisiologia , Receptores Opioides delta/química , Receptores Opioides mu/química , Animais , Linhagem Celular , Dimerização , Endocitose , Ala(2)-MePhe(4)-Gly(5)-Encefalina/farmacologia , D-Penicilina (2,5)-Encefalina/farmacologia , Humanos , Camundongos , Toxina Pertussis/farmacologia , Receptores Opioides delta/metabolismo , Receptores Opioides mu/metabolismo
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