| 1. |
- Aurelius, Oskar, et al.
(författare)
-
The Crystal Structure of Thermotoga maritima Class III Ribonucleotide Reductase Lacks a Radical Cysteine Pre-Positioned in the Active Site
- 2015
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:7
-
Tidskriftsartikel (refereegranskat)abstract
- Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides to deoxyribonucleotides, the building blocks for DNA synthesis, and are found in all but a few organisms. RNRs use radical chemistry to catalyze the reduction reaction. Despite RNR having evolved several mechanisms for generation of different kinds of essential radicals across a large evolutionary time frame, this initial radical is normally always channelled to a strictly conserved cysteine residue directly adjacent to the substrate for initiation of substrate reduction, and this cysteine has been found in the structures of all RNRs solved to date. We present the crystal structure of an anaerobic RNR from the extreme thermophile Thermotoga maritima (tmNrdD), alone and in several complexes, including with the allosteric effector dATP and its cognate substrate CTP. In the crystal structure of the enzyme as purified, tmNrdD lacks a cysteine for radical transfer to the substrate pre-positioned in the active site. Nevertheless activity assays using anaerobic cell extracts from T. maritima demonstrate that the class III RNR is enzymatically active. Other genetic and microbiological evidence is summarized indicating that the enzyme is important for T. maritima. Mutation of either of two cysteine residues in a disordered loop far from the active site results in inactive enzyme. We discuss the possible mechanisms for radical initiation of substrate reduction given the collected evidence from the crystal structure, our activity assays and other published work. Taken together, the results suggest either that initiation of substrate reduction may involve unprecedented conformational changes in the enzyme to bring one of these cysteine residues to the expected position, or that alternative routes for initiation of the RNR reduction reaction may exist. Finally, we present a phylogenetic analysis showing that the structure of tmNrdD is representative of a new RNR subclass IIIh, present in all Thermotoga species plus a wider group of bacteria from the distantly related phyla Firmicutes, Bacteroidetes and Proteobacteria.
|
|
| 2. |
- Gontero, Paolo, et al.
(författare)
-
Prognostic Factors and Risk Groups in T1G3 Non-Muscle-invasive Bladder Cancer Patients Initially Treated with Bacillus Calmette-Guerin : Results of a Retrospective Multicenter Study of 2451 Patients
- 2015
-
Ingår i: European Urology. - : Elsevier BV. - 0302-2838 .- 1873-7560. ; 67:1, s. 74-82
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The impact of prognostic factors in T1G3 non-muscle-invasive bladder cancer (BCa) patients is critical for proper treatment decision making. Objective: To assess prognostic factors in patients who received bacillus Calmette Guerin (BCG) as initial intravesical treatment of T1G3 tumors and to identify a subgroup of high-risk patients who should be considered for more aggressive treatment. Design, setting, and participants: Individual patient data were collected for 2451 T1G3 patients from 23 centers who received BCG between 1990 and 2011. Outcome measurements and statistical analysis: Using Cox multivariable regression, the prognostic importance of several clinical variables was assessed for time to recurrence, progression, BCa-specific survival, and overall survival (OS). Results and limitations: With a median follow-up of 5.2 yr, 465 patients (19%) progressed, 509 (21%) underwent cystectomy, and 221 (9%) died because of BCa. In multivariable analyses, the most important prognostic factors for progression were age, tumor size, and concomitant carcinoma in situ (CIS); the most important prognostic factors for BCa-specific survival and OS were age and tumor size. Patients were divided into four risk groups for progression according to the number of adverse factors among age >= 70 yr, size >= 3 cm, and presence of CIS. Progression rates at 10 yr ranged from 17% to 52%. BCa-specific death rates at 10 yr were 32% in patients >= 70 yr with tumor size >= 3 cm and 13% otherwise. Conclusions: T1G3 patients >= 70 yr with tumors >= 3 cm and concomitant CIS should be treated more aggressively because of the high risk of progression. Patient summary: Although the majority of T1G3 patients can be safely treated with intravesical bacillus Calmette-Guerin, there is a subgroup of T1G3 patients with age >= 70 yr, tumor size >= 3 cm, and concomitant CIS who have a high risk of progression and thus require aggressive treatment.
|
|
| 3. |
|
|
| 4. |
- Johansson, Renzo, et al.
(författare)
-
High-resolution crystal structures of the flavoprotein NrdI in oxidized and reduced states – an unusual flavodoxin
- 2010
-
Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 277:20, s. 4265-4277
-
Tidskriftsartikel (refereegranskat)abstract
- The small flavoprotein NrdI is an essential component of the class Ib ribonucleotide reductase system in many bacteria. NrdI interacts with the class Ib radical generating protein NrdF. It is suggested to be involved in the rescue of inactivated diferric centres or generation of active dimanganese centres in NrdF. Although NrdI bears a superficial resemblance to flavodoxin, its redox properties have been demonstrated to be strikingly different. In particular, NrdI is capable of two-electron reduction, whereas flavodoxins are exclusively one-electron reductants. This has been suggested to depend on a lesser destabilization of the negatively-charged hydroquinone state than in flavodoxins. We have determined the crystal structures of NrdI from Bacillus anthracis, the causative agent of anthrax, in the oxidized and semiquinone forms, at resolutions of 0.96 and 1.4 Å, respectively. These structures, coupled with analysis of all curated NrdI sequences, suggest that NrdI defines a new structural family within the flavodoxin superfamily. The conformational behaviour of NrdI in response to FMN reduction is very similar to that of flavodoxins, involving a peptide flip in a loop near the N5 atom of the flavin ring. However, NrdI is much less negatively charged than flavodoxins, which is expected to affect its redox properties significantly. Indeed, sequence analysis shows a remarkable spread in the predicted isoelectric points of NrdIs, from approximately pH 4–10. The implications of these observations for class Ib ribonucleotide reductase function are discussed.
|
|
| 5. |
- Johansson, Renzo, et al.
(författare)
-
Structural Mechanism of Allosteric Activity Regulation in a Ribonucleotide Reductase with Double ATP Cones
- 2016
-
Ingår i: Structure. - : Elsevier BV. - 0969-2126 .- 1878-4186. ; 24:6, s. 906-917
-
Tidskriftsartikel (refereegranskat)abstract
- Ribonucleotide reductases (RNRs) reduce ribonucleotides to deoxyribonucleotides. Their overall activity is stimulated by ATP and downregulated by dATP via a genetically mobile ATP cone domain mediating the formation of oligomeric complexes with varying quaternary structures. The crystal structure and solution X-ray scattering data of a novel dATP-induced homotetramer of the Pseudomonas aeruginosa class I RNR reveal the structural bases for its unique properties, namely one ATP cone that binds two dATP molecules and a second one that is non-functional, binding no nucleotides. Mutations in the observed tetramer interface ablate oligomerization and dATP-induced inhibition but not the ability to bind dATP. Sequence analysis shows that the novel type of ATP cone may be widespread in RNRs. The present study supports a scenario in which diverse mechanisms for allosteric activity regulation are gained and lost through acquisition and evolutionary erosion of different types of ATP cone.
|
|
| 6. |
- Karlberg, Tobias, et al.
(författare)
-
Porphyrin Binding and Distortion and Substrate Specificity in the Ferrochelatase Reaction: The Role of Active Site Residues.
- 2008
-
Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 1089-8638 .- 0022-2836. ; 378:5, s. 1074-1083
-
Tidskriftsartikel (refereegranskat)abstract
- The specific insertion of a divalent metal ion into tetrapyrrole macrocycles is catalyzed by a group of enzymes called chelatases. Distortion of the tetrapyrrole has been proposed to be an important component of the mechanism of metallation. We present the structures of two different inhibitor complexes: (1) N-methylmesoporphyrin (N-MeMP) with the His183Ala variant of Bacillus subtilis ferrochelatase; (2) the wild-type form of the same enzyme with deuteroporphyrin IX 2,4-disulfonic acid dihydrochloride (dSDP). Analysis of the structures showed that only one N-MeMP isomer out of the eight possible was bound to the protein and it was different from the isomer that was earlier found to bind to the wild-type enzyme. A comparison of the distortion of this porphyrin with other porphyrin complexes of ferrochelatase and a catalytic antibody with ferrochelatase activity using normal-coordinate structural decomposition reveals that certain types of distortion are predominant in all these complexes. On the other hand, dSDP, which binds closer to the protein surface compared to N-MeMP, does not undergo any distortion upon binding to the protein, underscoring that the position of the porphyrin within the active site pocket is crucial for generating the distortion required for metal insertion. In addition, in contrast to the wild-type enzyme, Cu(2+)-soaking of the His183Ala variant complex did not show any traces of porphyrin metallation. Collectively, these results provide new insights into the role of the active site residues of ferrochelatase in controlling stereospecificity, distortion and metallation.
|
|
| 7. |
- Kehoe, Laura, et al.
(författare)
-
Make EU trade with Brazil sustainable
- 2019
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 8. |
|
|
