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At least 127 records · Page 7Linked to original sources
PubMed2006

Down-regulation of radioresistance by LexA2 in Deinococcus radiodurans.

The extremely radioresistant bacterium Deinococcus radiodurans contains two LexA homologues (LexA1 and LexA2) that are possible transcriptional regulators associated with the DNA damage response. In this study, resequencing revealed that there was an additional cytosine nucleotide (nucleotide position 612) in the D. radiodurans lexA2 gene. Purified LexA2 possessed proteolytic activity that could be stimulated by RecA. In an effort to gain an insight into the role of LexA2 in the radiation response mechanism, recA, lexA1 and lexA2 disruptant strains were generated and investigated. The intracellular level of RecA increased in lexA1 and lexA2 disruptant strains following gamma-irradiation as in the wild-type strain. These results indicated that the two LexA homologues did not possess functional overlap regarding the induction of RecA. The lexA2 disruptant strains exhibited a much higher resistance to gamma-rays than the wild-type strain. Furthermore, a luciferase assay showed that pprA promoter activation was enhanced in the lexA2 disruptant strain following gamma-irradiation. The pprA gene encoding the novel radiation-inducible protein PprA plays a critical role in the radioresistance of D. radiodurans. The increase in radioresistance of the lexA2 disruptant strain is explained in part by the enhancement of pprA promoter activation.

Amino Acid Sequence↗
PubMed2003

Purification, crystallization and preliminary X-ray analysis of two nudix hydrolases from Deinococcus radiodurans.

Two nudix hydrolases from Deinococcus radiodurans have been purified and crystallized. Diffraction data have been collected to 1.4 and 1.9 A resolution for DR1025 and DR0079, respectively. DR1025 belongs to space group P4(1)2(1)2/P4(3)2(1)2, with unit-cell parameters a = b = 53.2, c = 122.6 A (unit-cell Volume 346 883 A(3), V(M) = 2.5 A(3) Da(-1), solvent content 50.2%). DR0079 belongs to space group C222(1), with unit-cell parameters a = 34.1, b = 157.2, c = 126.5 A (unit-cell Volume 677 308 A(3), V(M) = 2.2 A(3) Da(-1), solvent content 44.0%). The calculated cell content of DR1025 indicates the presence of one molecule in the asymmetric unit. Dynamic light scattering and gel filtration suggest it to be a dimer in solution. The space group and unit-cell parameters of DR0079 indicate the presence of two molecules per asymmetric unit. Gel filtration and NMR spectroscopy suggest it to be a monomer in solution.

Amino Acid Sequence↗
PubMed2004

Crystallization and preliminary X-ray crystallographic analysis of the RecR protein from Deinococcus radiodurans, a member of the RecFOR DNA-repair pathway.

The RecR protein plays a key role in the RecFOR pathway of recombination, which is necessary for the repair of ssDNA gaps. RecR from Deinococcus radiodurans has been overexpressed in Escherichia coli and crystallized at 297 K using polyethylene glycol 1000 as a precipitant. X-ray diffraction data to 2.90 A resolution have been collected at 100 K using Cu Kalpha X-rays from a mercury-soaked crystal. The crystal belongs to space group C222(1), with unit-cell parameters a = 106.96, b = 122.25, c = 156.01 A. The asymmetric unit contains four monomers of RecR, with a crystal volume per protein weight (V(M)) of 2.57 A(3) Da(-1) and a solvent content of 51.0%.

Bacterial Proteins↗
PubMed2004

Expression, purification, crystallization and preliminary crystal structure analysis of the Deinococcus radiodurans organic hydroperoxide-resistance protein.

The organic hydroperoxide-resistance protein (DR1857) from Deinococcus radiodurans has been expressed, purified and crystallized. The crystals are suitable for X-ray analysis, diffract to at least 2.3 A resolution, have unit-cell parameters a = 45.7, b = 59.6, c = 49.7 A, beta = 90.43 degrees and belong to space group P2(1). The calculated Matthews coefficient of 2.1 A(3) Da(-1) coupled with a calculated solvent content of approximately 42% is consistent with the presence of a homodimer in the asymmetric unit. Here, the methods used in the overexpression and purification of the protein are described and details of crystallization conditions and preliminary X-ray diffraction are provided.

Bacterial Proteins↗
PubMed2004

Crystallization and preliminary X-ray crystallographic analysis of a putative agmatinase from Deinococcus radiodurans.

Agmatine, which results from the decarboxylation of arginine by arginine decarboxylase, is a metabolic intermediate in the biosynthesis of putresine and higher polyamines. The enzyme agmatinase catalyses the hydrolysis of agmatine to putresine and urea. Recent studies indicate that agmatinase plays important roles in mammals. Human mitochondrial agmatinase shows a considerable level of sequence similarity to bacterial agmatinases, including a putative agmatinase from Deinococcus radiodurans. The putative agmatinase from D. radiodurans has been overexpressed in Escherichia coli and crystallized at 297 K using polyethylene glycol 3000 as a precipitant. X-ray diffraction data were collected to 1.80 A from a crystal grown in the presence of Mn2+ and 1,6-hexanediamine. The crystals are orthorhombic, belonging to the space group P2(1)2(1)2(1), with unit-cell parameters a = 81.77, b = 131.44, c = 168.85 A, alpha = beta = gamma = 90 degrees. A hexameric molecule is likely to be present in the asymmetric unit, giving a crystal volume per protein weight (VM) of 2.15 A3 Da(-1) and a solvent content of 41.8%.

Crystallization↗
PubMed2004

Crystallization and preliminary X-ray characterization of the atypical glutaminyl-tRNA synthetase from Deinococcus radiodurans.

The glutaminyl-tRNA synthetase (GlnRS) from the radiation-resistant bacterium Deinococcus radiodurans differs from known GlnRSs and other tRNA synthetases by the presence of an additional C-terminal domain resembling the C-terminal region of the GatB subunit of tRNA-dependent amidotransferase (AdT). This atypical synthetase was overexpressed in Escherichia coli, purified and crystallized in the presence of PEG 3350. Orthorhombic crystals were obtained that belong to space group P2(1)2(1)2(1) and diffract to 2.3 A resolution. The crystal structure was solved by molecular replacement using the structure of E. coli GlnRS as a search model.

Amino Acyl-tRNA Synthetases↗
PubMed2005

Structure of the uracil-DNA N-glycosylase (UNG) from Deinococcus radiodurans.

Uracil-DNA glycosylases are DNA-repair enzymes that catalyse the removal of promutagenic uracil from single- and double-stranded DNA, thereby initiating the base-excision repair (BER) pathway. Uracil in DNA can occur by mis-incorporation of dUMP in place of dTMP during DNA synthesis or by deamination of cytosine, resulting in U-A or U-G mispairs. The radiation-resistant bacterium Deinococcus radiodurans has an elevated number of uracil-DNA glycosylases compared with most other organisms. The crystal structure of dr0689 (uracil-DNA N-glycosylase), which has been shown to be the major contributor to the removal of mis-incorporated uracil bases in crude cell extracts of D. radiodurans, is reported.

Amino Acid Sequence↗
PubMed2006

Structure of the manganese superoxide dismutase from Deinococcus radiodurans in two crystal forms.

The structure of the manganese superoxide dismutase (Mn-SOD; DR1279) from Deinococcus radiodurans has been determined in two different crystal forms. Both crystal forms are monoclinic with space group P2(1). Form I has unit-cell parameters a = 44.28, b = 83.21, c = 59.52 angstroms, beta = 110.18 degrees and contains a homodimer in the asymmetric unit, with structure refinement (R = 16.8%, R(free) = 23.6%) carried out using data to d(min) = 2.2 angstroms. Form II has unit-cell parameters a = 43.57, b = 87.10, c = 116.42 angstroms, beta = 92.1 degrees and an asymmetric unit containing two Mn-SOD homodimers; structure refinement was effected to a resolution of 2.0 angstroms (R = 17.2%, R(free) = 22.3%). The resulting structures are compared with that of Mn-SOD from Escherichia coli, with which they are shown to be essentially isostructural.

Crystallography, X-Ray↗
PubMed2006

Expression, purification, crystallization and preliminary X-ray crystallographic studies of Deinococcus radiodurans thioredoxin reductase.

Deinococcus radiodurans, a Gram-positive bacterium capable of withstanding extreme ionizing radiation, contains two thioredoxins (Trx and Trx1) and a single thioredoxin reductase (TrxR) as part of its response to oxidative stress. Thioredoxin reductase is a member of the family of pyridine nucleotide-disulfide oxidoreductase flavoenzymes. Recombinant D. radiodurans TrxR with a His tag at the N-terminus was expressed in Escherichia coli and purified by metal-affinity chromatography. The protein was crystallized using the sitting-drop vapour-diffusion method in the presence of 35% PEG 4000, 0.2 M ammonium acetate and citric acid buffer pH 5.1 at 293 K. X-ray diffraction data were collected on a cryocooled crystal to a resolution of 1.9 angstroms using a synchrotron-radiation source. The space group was determined to be P3(2)21, with unit-cell parameters a = b = 84.33, c = 159.88 angstroms. The structure of the enzyme has been solved by molecular-replacement methods and structure refinement is in progress.

Base Sequence↗
PubMed2004

Involvement of an X family DNA polymerase in double-stranded break repair in the radioresistant organism Deinococcus radiodurans.

DNA polymerases of the X family have been implicated in a variety of DNA repair processes in eukaryotes. Here we show that Deinococcus radiodurans, a highly radioresistant bacterium able to mend hundreds of radiation-induced double-stranded DNA breaks, expresses a DNA polymerase belonging to the X family. This novel bacterial polymerase, named PolX(Dr), was identified as the product of the Deinococcal DR0467 gene. The purified PolX(Dr) protein possesses a DNA polymerase activity that is stimulated by MnCl2, a property of the X family DNA polymerases. Antibodies raised against PolX(Dr) recognized human pol lambda, rat pol beta and yeast Pol4 and, conversely, antibodies raised against these proteins recognized PolX(Dr). This immunological cross-reactivity suggests a high degree of structural conservation among the polymerases of the X family. Lack of PolX(Dr) reduced the rate of repair of double-stranded DNA breaks and increased cell sensitivity to gamma-rays. PolX(Dr) thus appears to play an important role in double-stranded DNA break repair in D. radiodurans.

Animals↗
PubMed2004

PprA: a novel protein from Deinococcus radiodurans that stimulates DNA ligation.

The extraordinary radiation resistance of Deinococcus radiodurans results from the efficient capacity of the bacterium to repair DNA double-strand breaks. By analysing the DNA damage repair-deficient mutant, KH311, a unique radiation-inducible gene (designated pprA) responsible for loss of radiation resistance was identified. Investigations in vitro showed that the gene product of pprA (PprA) preferentially bound to double-stranded DNA carrying strand breaks, inhibited Escherichia coli exonuclease III activity, and stimulated the DNA end-joining reaction catalysed by ATP-dependent and NAD-dependent DNA ligases. These results suggest that D. radiodurans has a radiation-induced non-homologous end-joining repair mechanism in which PprA plays a critical role.

Amino Acid Sequence↗
PubMed2004

Inhibition of peptide bond formation by pleuromutilins: the structure of the 50S ribosomal subunit from Deinococcus radiodurans in complex with tiamulin.

Tiamulin, a prominent member of the pleuromutilin class of antibiotics, is a potent inhibitor of protein synthesis in bacteria. Up to now the effect of pleuromutilins on the ribosome has not been determined on a molecular level. The 3.5 A structure of the 50S ribosomal subunit from Deinococcus radiodurans in complex with tiamulin provides for the first time a detailed picture of its interactions with the 23S rRNA, thus explaining the molecular mechanism of the antimicrobial activity of the pleuromutilin class of antibiotics. Our results show that tiamulin is located within the peptidyl transferase center (PTC) of the 50S ribosomal subunit with its tricyclic mutilin core positioned in a tight pocket at the A-tRNA binding site. Also, the extension, which protrudes from its mutilin core, partially overlaps with the P-tRNA binding site. Thereby, tiamulin directly inhibits peptide bond formation. Comparison of the tiamulin binding site with other PTC targeting drugs, like chloramphenicol, clindamycin and streptogramins, may facilitate the design of modified or hybridized drugs that extend the applicability of this class of antibiotics.

Crystallography, X-Ray↗
PubMed2005

HspR is a global negative regulator of heat shock gene expression in Deinococcus radiodurans.

The HspR protein functions as a negative regulator of chaperone and protease gene expression in a diversity of bacteria. Here we have identified, cloned and deleted the Deinococcus radiodurans HspR homologue, DR0934. Delta hspR mutants exhibit moderate growth defects when shifted to mild heat shock temperatures, but are severely impaired for survival at 48 degrees C. Using quantitative reverse transcription polymerase chain reaction and global transcriptional analysis, we have identified 14 genes that are derepressed in the absence of stress in the delta hspR background, 11 of which encode predicted chaperones and proteases, including dnaKJgrpE, ftsH, lonB, hsp20 and clpB. Promoter mapping indicated that the transcription of these genes initiates from a promoter bearing a sigma70-type consensus, and that putative HspR binding sites (HAIR) were present in the 5'-untranslated regions. Electrophoretic mobility shift assays indicated that HspR binds to these promoters at the HAIR site in vitro. These results strongly suggest that DR0934 encodes the HspR-like global negative regulator of D. radiodurans that directly represses chaperone and protease gene expression by binding to the HAIR site in close proximity to promoter regions.

5' Untranslated Regions↗
PubMed2006

Mutagenesis via IS transposition in Deinococcus radiodurans.

Analysis of the complete genome indicates that insertion sequences (ISs) are abundant in the radio-resistant bacterium Deinococcus radiodurans. By developing a forward mutagenesis assay to detect any inactivation events in D. radiodurans, we found that in the presence of an active mismatch repair system 75% of the mutations to trimethoprim-resistance (Tmp(R)) resulted from an IS insertion into the thyA coding region. Analysis of their distribution among the spontaneous Tmp(R) mutants indicated that five different ISs were transpositionally active. A type II Miniature Inverted-repeat Transposable Element (MITE), related to one of the deinococcal ISs, was also discovered as an insertion into thyA. Seven additional genomic copies of this MITE element were identified by BLASTN. Gamma-ray irradiation of D. radiodurans led to an increase of up to 10-fold in the frequency of Tmp(R) mutants. Analysis of the induced mutations in cells exposed to 10 kGy indicated that gamma-irradiation induced transposition of ISDra2 approximately 100-fold. A 50-fold induction of ISDra2 transposition was also observed in cells exposed to 600 J m(-2) UV-irradiation. Point mutations to rifampicin resistance (Rif(R)) were also induced by gamma-irradiation to reach a plateau at 2 kGy. The plateau value represented a 16-fold increase in the mutant frequency over the background. Although error-free repair strategies predominate in D. radiodurans, an upregulation of transposition, as well as induction of point mutations in cells recovering from DNA damage, provide a genetic variability that may have long-term evolutionary consequences on the fitness of this organism in its habitat.

Bacterial Proteins↗
PubMed2006

Limited concentration of RecA delays DNA double-strand break repair in Deinococcus radiodurans R1.

To evaluate the importance of RecA in DNA double-strand break (DSB) repair, we examined the effect of low and high RecA concentrations such as 2500 and 100 000 molecules per cell expressed from the inducible Pspac promoter in Deinococcus radiodurans in absence or in presence of IPTG respectively. We showed that at low concentration, RecA has a negligible effect on cell survival after gamma-irradiation when bacteria were immediately plated on TGY agar whereas it significantly decreased the survival to gamma-irradiation of DeltaddrA cells while overexpression of RecA can partially compensate the loss of DdrA protein. In contrast, when cells expressing limited concentration of RecA were allowed to recover in TGY2X liquid medium, they showed a delay in mending DSB, failed to reinitiate DNA replication and were committed to die during incubation. A deletion of irrE resulted in sensitivity to gamma-irradiation and mitomycin C treatment. Interestingly, constitutive high expression of RecA compensates partially the DeltairrE sensitization to mitomycin C. The cells with low RecA content also failed to cleave LexA after DNA damage. However, neither a deletion of the lexA gene nor the expression of a non-cleavable LexA(Ind-) mutant protein had an effect on survival or kinetics of DNA DSB repair compared with their lexA+ counterparts in recA+ as well as in bacteria expressing limiting concentration of RecA, suggesting an absence of relationship between the absence of LexA cleavage and the loss of viability or the delay in the kinetics of DSB repair. Thus, LexA protein seems to play no major role in the recovery processes after gamma-irradiation in D. radiodurans.

Bacterial Proteins↗
PubMed2006

DNA polymerase X from Deinococcus radiodurans possesses a structure-modulated 3'-->5' exonuclease activity involved in radioresistance.

Recently a family X DNA polymerase (PolXDr) was identified in the radioresistant bacterium Deinococcus radiodurans. Knockout cells show a delay in double-strand break repair (DSBR) and an increased sensitivity to gamma-irradiation. Here we show that PolXDr possesses 3'-->5' exonuclease activity that stops cutting close to a loop. PolXDr consists of a DNA polymerase X domain (PolXc) and a Polymerase and Histidinol Phosphatase (PHP) domain. Deletion of the PHP domain abolishes only the structure-modulated but not the canonical 3'-->5' exonuclease activity. Thus, the exonuclease resides in the PolXc domain, but the structure-specificity requires additionally the PHP domain. Mutation of two conserved glycines in the PolXc domain leads to a specific loss of the structure-modulated exonuclease activity but not the exonuclease activity in general. The PHP domain itself does not show any activity. PolXDr is the first family X DNA polymerase that harbours an exonuclease activity. The wild-type protein, the glycine mutant and the two domains were expressed separately in DeltapolXDr cells. The wild-type protein could restore the radiation resistance, whereas intriguingly the mutant proteins showed a significant negative effect on survival of gamma-irradiated cells. Taken together our in vivo results suggest that both PolXDr domains play important roles in DSBR in D. radiodurans.

DNA↗
PubMed2006

Internal promoter characterization and expression of the Deinococcus radiodurans pprI-folP gene cluster.

PprI is a general gene switch responsible for the extraordinary radioresistance of Deinococcus radiodurans. From NCBI DNA sequence analysis, it was predicted that the translation start codon of the downstream folP (DR0168) gene overlaps the pprI (DR0167) stop codon, suggesting that these genes may form an operon. In this study, we show that a mutant containing an inserted sequence in folP does not grow unless folate is added to the medium, but is not affected in extreme radioresistance, whereas a pprI disruptant strain could grow in the absence of folate. It was found that expression of a pprI-lacZ fusion is constitutive and unaltered following ionizing radiation as is the production of the PprI protein. PprI protein is not expressed if its promoter is deleted and the transcription from the entire pprI promoter is essential for radioresistance of D. radiodurans. However, the deletion of pprI promoter has no effect on the expression of the folP-lacZ fusion. Primer extension analysis of the folP promoter region shows that folP is transcribed from its own promoter located within the pprI structural gene. All these results do support neither the existence of a pprI-folP operon nor a regulatory role of FolP in pprI expression.

Bacterial Proteins↗
PubMed2003

Ringlike structure of the Deinococcus radiodurans genome: a key to radioresistance?

The bacterium Deinococcus radiodurans survives ionizing irradiation and other DNA-damaging assaults at doses that are lethal to all other organisms. How D. radiodurans accurately reconstructs its genome from hundreds of radiation-generated fragments in the absence of an intact template is unknown. Here we show that the D. radiodurans genome assumes an unusual toroidal morphology that may contribute to its radioresistance. We propose that, because of restricted diffusion within the tightly packed and laterally ordered DNA toroids, radiation-generated free DNA ends are held together, which may facilitate template-independent yet error-free joining of DNA breaks.

Chromatin↗