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1.
Nature ; 555(7695): 260-264, 2018 03 08.
Artigo em Inglês | MEDLINE | ID: mdl-29489748

RESUMO

PIWI-interacting RNAs (piRNAs) are small regulatory RNAs that bind to PIWI proteins to control transposons and maintain genome integrity in animal germ lines. piRNA 3' end formation in the silkworm Bombyx mori has been shown to be mediated by the 3'-to-5' exonuclease Trimmer (Trim; known as PNLDC1 in mammals), and piRNA intermediates are bound with PIWI anchored onto mitochondrial Tudor domain protein Papi. However, it remains unclear whether the Zucchini (Zuc) endonuclease and Nibbler (Nbr) 3'-to-5' exonuclease, both of which have pivotal roles in piRNA biogenesis in Drosophila, are required for piRNA processing in other species. Here we show that the loss of Zuc in Bombyx had no effect on the levels of Trim and Nbr, but resulted in the aberrant accumulation of piRNA intermediates within the Papi complex, and that these were processed to form mature piRNAs by recombinant Zuc. Papi exerted its RNA-binding activity only when bound with PIWI and phosphorylated, suggesting that complex assembly involves a hierarchical process. Both the 5' and 3' ends of piRNA intermediates within the Papi complex showed hallmarks of PIWI 'slicer' activity, yet no phasing pattern was observed in mature piRNAs. The loss of Zuc did not affect the 5'- and 3'-end formation of the intermediates, strongly supporting the idea that the 5' end of Bombyx piRNA is formed by PIWI slicer activity, but independently of Zuc, whereas the 3' end is formed by the Zuc endonuclease. The Bombyx piRNA biogenesis machinery is simpler than that of Drosophila, because Bombyx has no transcriptional silencing machinery that relies on phased piRNAs.


Assuntos
Bombyx/citologia , Bombyx/genética , Endorribonucleases/metabolismo , Células Germinativas/metabolismo , Proteínas Mitocondriais/metabolismo , RNA Interferente Pequeno/biossíntese , Animais , Proteínas Argonautas/metabolismo , Drosophila , RNA Interferente Pequeno/genética
2.
EMBO Rep ; 22(4): e51313, 2021 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-33555135

RESUMO

The piRNA amplification pathway in Bombyx is operated by Ago3 and Siwi in their piRISC form. The DEAD-box protein, Vasa, facilitates Ago3-piRISC production by liberating cleaved RNAs from Siwi-piRISC in an ATP hydrolysis-dependent manner. However, the Vasa-like factor facilitating Siwi-piRISC production along this pathway remains unknown. Here, we identify DEAD-box polypeptide 43 (DDX43) as the Vasa-like protein functioning in Siwi-piRISC production. DDX43 belongs to the helicase superfamily II along with Vasa, and it contains a similar helicase core. DDX43 also contains a K-homology (KH) domain, a prevalent RNA-binding domain, within its N-terminal region. Biochemical analyses show that the helicase core is responsible for Ago3-piRISC interaction and ATP hydrolysis, while the KH domain enhances the ATPase activity of the helicase core. This enhancement is independent of the RNA-binding activity of the KH domain. For maximal DDX43 RNA-binding activity, both the KH domain and helicase core are required. This study not only provides new insight into the piRNA amplification mechanism but also reveals unique collaborations between the two domains supporting DDX43 function within the pathway.


Assuntos
Bombyx , RNA Helicases DEAD-box , Animais , Bombyx/genética , RNA Helicases DEAD-box/genética , Peptídeos/genética , RNA Interferente Pequeno/genética
3.
BMC Musculoskelet Disord ; 24(1): 965, 2023 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-38087214

RESUMO

BACKGROUND: Bicruciate-retaining (BCR) prosthesis has been introduced to recreate normal knee movement by preserving both the anterior and posterior cruciate ligaments. However, the use of BCR total knee arthroplasty (TKA) is still debatable because of several disappointing reports. We have been performing BCR TKAs with personalized alignment (PA). This study aimed to reveal the limb alignment and soft tissue balance of FA-BCR TKAs and compare the clinical outcomes of FA-BCR TKAs with those of unicompartmental knee arthroplasty (UKA). METHODS: Fifty BCR TKAs and 58 UKAs were included in this study. The joint component gaps of BCR TKA were evaluated intraoperatively and the postoperative hip-knee-ankle (HKA) angle, medial proximal tibial angle (MPTA), and lateral distal femoral angle (LDFA) were measured using full-length standing radiography. The short-term clinical outcomes of BCR TKAs were compared with those of UKA using the scoring system of 2011 Knee Society Scoring (KSS) and the knee injury and osteoarthritis outcome score (KOOS) at an average of 2 years postoperatively (1-4yeras). RESULTS: The coronal alignment values of PA-BCR TKA were as follows: HKA angle, 177.9° ± 2.3°; MPTA, 85.4° ± 1.9°; and LDFA, 87.5° ± 1.9°. The joint component gaps at flexion angles of 10°, 30°, 60°, and 90° were 11.1 ± 1.2, 10.9 ± 1.4, 10.7 ± 1.3, and 11.2 ± 1.4 mm for the medial compartment and 12.9 ± 1.5, 12.6 ± 1.8, 12.5 ± 1.8 and 12.5 ± 1.7 mm for the lateral compartment, respectively. The patient expectation score and maximum extension angle of PA-BCR TKA were significantly better than those of UKAs. CONCLUSIONS: The short-term clinical outcomes of PA-BCR TKA were comparable or a slightly superior to those of UKAs.


Assuntos
Artroplastia do Joelho , Prótese do Joelho , Osteoartrite do Joelho , Ligamento Cruzado Posterior , Humanos , Artroplastia do Joelho/métodos , Articulação do Joelho/diagnóstico por imagem , Articulação do Joelho/cirurgia , Joelho/cirurgia , Ligamento Cruzado Posterior/diagnóstico por imagem , Ligamento Cruzado Posterior/cirurgia , Osteoartrite do Joelho/diagnóstico por imagem , Osteoartrite do Joelho/cirurgia , Estudos Retrospectivos
4.
Knee Surg Sports Traumatol Arthrosc ; 31(12): 5681-5689, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37884728

RESUMO

PURPOSE: Patellofemoral (PF) compartment cartilage lesions are a frequent problem after anterior cruciate ligament (ACL) reconstruction. This study aimed to determine the factors that influence PF cartilage lesions after anatomical ACL reconstruction. METHODS: This study enrolled a total of 114 patients who did not manifest PF compartment cartilage lesions during anatomical ACL reconstruction and underwent second-look arthroscopy 18 months postoperatively. Arthroscopy using the International Cartilage Repair Society (ICRS) classification was used to assess cartilage lesions. The correlation between surgical findings, radiographic factors, and clinical factors and change of ICRS grade was analysed. Multivariate regression analysis was conducted to reveal the independent risk factors for PF cartilage lesions among patients' demographic data and parameters that correlated with the change of ICRS grade in the correlation analyses. RESULTS: ICRS grade changes in PF cartilage were significantly correlated with age, sex, quadriceps strength at 1 year postoperatively, hamstrings strength at pre- and 1 year postoperatively, and single leg hop test at 1 year postoperatively. However, no significant correlation was found between the time between injury and surgery, posterior tibial slope angle, pre- and postoperative Tegner activity scale, graft type, initial graft tension, meniscus injury, meniscus injury treatment, pre- and postoperative range of motion, anteroposterior laxity and preoperative quadriceps strength, and the change in ICRS grade. Multivariate regression analysis revealed male (P = 0.019) and quadriceps strength weakness at 1 year postoperatively (P = 0.009) as independent risk factors for PF cartilage lesions. CONCLUSIONS: Quadriceps strength weakness 1 year after ACL reconstruction and males were correlated with a new PF cartilage lesion after anatomical ACL reconstruction, with no significant correlation between bone-patellar tendon-bone autograft, initial graft tension, or extension deficit and new PF cartilage lesion. Rehabilitation that focuses on quadriceps strength after ACL reconstruction is recommended to prevent new PF cartilage lesions. LEVEL OF EVIDENCE: Level IV.


Assuntos
Lesões do Ligamento Cruzado Anterior , Reconstrução do Ligamento Cruzado Anterior , Cartilagem Articular , Humanos , Masculino , Cartilagem Articular/cirurgia , Lesões do Ligamento Cruzado Anterior/complicações , Lesões do Ligamento Cruzado Anterior/cirurgia , Músculo Quadríceps/cirurgia , Reconstrução do Ligamento Cruzado Anterior/efeitos adversos , Reconstrução do Ligamento Cruzado Anterior/reabilitação , Fatores de Risco
5.
Arch Orthop Trauma Surg ; 143(4): 1949-1955, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35235029

RESUMO

INTRODUCTION: Although intramedullary screw fixation likely leads to successful union of Jones fractures compared to that of nonoperative treatments, bony union disorder after surgical treatment remains to be elucidated. METHODS: Intramedullary screw fixation was performed for the surgical treatment of proximal fifth metatarsal stress fractures in this series. Between January 2008 and December 2019, the feet of 222 patients were investigated regarding the effective factors for postoperative bony union between the normal union group and the bony union disorder group according to the patients' physical status, radiological assessment, and screw size. The mean postoperative follow-up period was 11.1 months. Bone union disorder was defined as delayed union, nonunion, or a re-fracture recognized through a radiographic image. RESULTS: The prevalence rate of union disorders occurred in 14% (31/222) of the patients. The risk of bone union disorder significantly increased when using a small-diameter screw (odds ratio 4.81, 95% confidence interval [CI] 1.62-14.2, p = 0.004) and non-bone graft procedures (odds ratio 3.13, 95% CI 1.22-8.02, p = 0.02). Screw length, preoperative Torg's classification, or patients' physical status did not affect postoperative bony union. CONCLUSIONS: Approximately 14.0% of the patients in our study had postoperative bone union disorder. Small-diameter screws and non-bone graft procedures increased the risk of bone union disorder in the intramedullary screw fixation technique of fifth metatarsal bone stress fractures. LEVEL OF EVIDENCE: Level 4, case series.


Assuntos
Doenças Ósseas , Fraturas de Estresse , Ossos do Metatarso , Humanos , Ossos do Metatarso/cirurgia , Fixação Interna de Fraturas/métodos , Parafusos Ósseos
6.
Eur J Orthop Surg Traumatol ; 33(2): 361-366, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34988722

RESUMO

BACKGROUND: Return to sports is one of the important reasons why athletes with an anterior cruciate ligament (ACL) injury undergo surgery. There are few reports on return to sports among adult amateur athletes (individuals older than the college age who participate in competitive sports). This study aimed to investigate the return of adult amateur athletes to competitive sports 1 year after ACL reconstruction and to identify the indicators for return to competitive sports. METHODS: Between January 2015 and December 2017, adult amateur athletes who underwent primary ACL reconstruction were retrospectively investigated. The rate of return to competitive sports 1 year after surgery was evaluated. The patients were categorized into two groups: return to sports group (R group) and non-return to sports group (N group). Pre- and postoperative range of motion, pivot-shift test, anteroposterior laxity, quadriceps strength, Lysholm score, and the International Knee Documentation Committee score were compared between the groups. RESULTS: This study included 78 patients (48 men, 30 women; age range, 22-53 years). Five months after ACL reconstruction, quadriceps strength was significantly lower in the N group than in the R group, denoting muscle weakness in the N group at that time. No significant differences were found in the other items between the groups preoperatively and 1 year after surgery. CONCLUSION: In this study, the rate of return to competitive sports of adult amateur athletes 1 year after ACL reconstruction was 76.9%. Quadriceps strength may be an early indicator of return to competitive sports 1 year after reconstruction.


Assuntos
Lesões do Ligamento Cruzado Anterior , Reconstrução do Ligamento Cruzado Anterior , Masculino , Humanos , Adulto , Feminino , Adulto Jovem , Pessoa de Meia-Idade , Estudos Retrospectivos , Recuperação de Função Fisiológica , Articulação do Joelho/cirurgia , Atletas , Lesões do Ligamento Cruzado Anterior/cirurgia
7.
J Foot Ankle Surg ; 61(4): 807-811, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34973864

RESUMO

Surgery with autologous bone grafting for proximal fifth metatarsal diaphyseal stress fracture has a potential to decrease nonunion, but it is not performed widely as the primary surgery because of donor-site morbidity. We have devised and performed a less invasive surgical procedure with autologous bone grafting and aimed to investigate the clinical and radiologic outcomes of this procedure. The data for 73 patients who underwent primary intramedullary screw fixation with autologous bone grafting from the fifth metatarsal base for proximal fifth metatarsal diaphyseal stress fractures were investigated retrospectively. The clinical and radiologic outcomes were evaluated. The mean time to bone union, starting running, and return to play was 11.8, 6.3, and 13.4 weeks, respectively. Bone union was achieved in 76 of the 78 cases. Intramedullary screw fixation with autologous bone grafting from the fifth metatarsal base showed good outcomes. It may be a useful surgical option for patients with proximal fifth metatarsal diaphyseal stress fractures.


Assuntos
Doenças Ósseas , Doenças das Cartilagens , Fraturas Ósseas , Fraturas de Estresse , Ossos do Metatarso , Transplante Ósseo/métodos , Fixação Interna de Fraturas/métodos , Fraturas Ósseas/cirurgia , Fraturas de Estresse/diagnóstico por imagem , Fraturas de Estresse/cirurgia , Humanos , Ossos do Metatarso/diagnóstico por imagem , Ossos do Metatarso/cirurgia , Estudos Retrospectivos
8.
BMC Musculoskelet Disord ; 22(1): 725, 2021 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-34425817

RESUMO

BACKGROUND: Intramedullary screw fixation is considered the standard treatment for proximal fifth metatarsal stress fractures. Low-intensity pulsed ultrasound (LIPUS) is a well-known bone-healing enhancement device. However, to the best of our knowledge, no clinical study has focused on the effect of LIPUS for postoperative bone union in proximal fifth metatarsal stress fractures. This study aimed to investigate the effect of LIPUS treatment after intramedullary screw fixation for proximal fifth metatarsal stress fractures. METHODS: Between January 2015 and March 2020, patients who underwent intramedullary screw fixation for proximal fifth metatarsal stress fractures were investigated retrospectively. All patients underwent intramedullary screw fixation using a headless compression screw with autologous bone grafts from the base of the fifth metatarsal. The time to restart running and return to sports, as well as that for radiographic bone union, were compared between groups with or without LIPUS treatment. LIPUS treatment was initiated within 3 weeks of surgery in all cases. RESULTS: Of the 101 ft analyzed, 57 ft were assigned to the LIPUS treatment group, and 44 ft were assigned to the non-LIPUS treatment group. The mean time to restart running and return to sports was 6.8 and 13.7 weeks in the LIPUS treatment group and was 6.2 and 13.2 weeks in the non-LIPUS treatment group, respectively. There were no significant differences in these parameters between groups. In addition, the mean time to radiographic bone union was not significantly different between the LIPUS treatment group (11.9 weeks) and the non-LIPUS treatment group (12.0 weeks). The rate of postoperative nonunion in the LIPUS treatment group was 0% (0/57), while that in the non-LIPUS treatment group was 4.5% (2/44). However, this difference was not statistically significant. CONCLUSIONS: There were no statistically significant differences regarding the time to start running, return to sports, and radiographic bone union in patients with or without LIPUS treatment after intramedullary screw fixation for proximal fifth metatarsal stress fractures. Therefore, we cannot recommend the routine use of LIPUS to shorten the time to bone union after intramedullary screw fixation for proximal fifth metatarsal stress fractures.


Assuntos
Fraturas de Estresse , Ossos do Metatarso , Parafusos Ósseos , Fixação Interna de Fraturas , Fraturas de Estresse/diagnóstico por imagem , Fraturas de Estresse/cirurgia , Humanos , Ossos do Metatarso/diagnóstico por imagem , Ossos do Metatarso/cirurgia , Estudos Retrospectivos , Ondas Ultrassônicas
9.
Chem Pharm Bull (Tokyo) ; 69(9): 892-895, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34470953

RESUMO

The synthesis of 2,2-dimethyloxepane frameworks based on the 7-endo-trig cyclization of ene-diol using a catalytic amount of metal catalysts (Au, Ag) or Brønsted acid (TfOH) has been developed. Also, the spiro-type dioxabicyclic products were also derived from the diene-diols. For the condition using metal catalysts, the cyclization selectively reacted between the 1,1,3-trisubstituted alkenes and alcohols to form the 2,2-dimethyloxepane frameworks. On the other hand, the TfOH reacted with not only the 1,1,2-trisubstituted alkene, but also the 1-substituted and 1,2-disubstituted alkenes providing the corresponding cyclic ethers, which is quite different from the conditions of the metal catalysts.


Assuntos
Ouro/química , Mesilatos/química , Oxepinas/síntese química , Prata/química , Catálise , Ciclização , Estrutura Molecular , Oxepinas/química
10.
Eur J Neurosci ; 51(3): 822-839, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31834948

RESUMO

State-dependent modulation of sensory systems has been studied in many organisms and is possibly mediated through neuromodulators such as monoamine neurotransmitters. Among these, dopamine is involved in many aspects of animal behaviour, including movement control, attention, motivation and cognition. However, the precise neural mechanism underlying dopaminergic modulation of behaviour induced by sensory stimuli remains poorly understood. Here, we used Drosophila melanogaster to show that dopamine can modulate the optomotor response to moving visual stimuli including noise. The optomotor response is the head-turning response to moving objects, which is observed in most sight-reliant animals including mammals and insects. First, the effects of the dopamine system on the optomotor response were investigated in mutant flies deficient in dopamine receptors D1R1 or D1R2, which are involved in the modulation of sleep-arousal in flies. We examined the optomotor response in D1R1 knockout (D1R1 KO) and D1R2 knockout (D1R2 KO) flies and found that it was not affected in D1R1 KO flies; however, it was significantly reduced in D1R2 KO flies compared with the wild type. Using cell-type-specific expression of an RNA interference construct of D1R2, we identified the fan-shaped body, a part of the central complex, responsible for dopamine-mediated modulation of the optomotor response. In particular, pontine cells in the fan-shaped body seemed important in the modulation of the optomotor response, and their neural activity was required for the optomotor response. These results suggest a novel role of the central complex in the modulation of a behaviour based on the processing of sensory stimulations.


Assuntos
Dopamina , Drosophila melanogaster , Animais , Comportamento Animal , Receptores Dopaminérgicos , Sono
11.
J Mater Sci Mater Med ; 30(5): 57, 2019 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-31087211

RESUMO

In this paper, we study a process for modifying the surface microtopography of the Ti oxide layer using a nanosecond-pulsed laser (NPL). Even now, the mechanism by which hydroxyl groups are generated on the titanium surface treated by NPL is not clear. Hence, we evaluated the surface properties of the NPL defocus distances on pure titanium surfaces, and investigated the relationship between the generation of hydroxyapatites/cell viability and the titanium surface characteristics. The NPL defocus distance was varied from 0 to 4 mm. Defocus distances of 0 and 2 mm generated microtopographical features on the titanium surface, and the resulting surfaces exhibited a greater density of OH groups than the surface treated with a defocus distance of 4 mm. The surfaces treated using defocus distances of 0 and 2 mm were found to be coated with microspherical hydroxyapatite composed of coexisting plate- and needle-like crystals after immersion in simulated body fluid, and alkaline phosphatase activity assays indicated improved cell compatibility. The improvements in biocompatibility and cell compatibility were due to the pocket-like microtopographical structures formed along the processing trace. These pockets contained a large amount of OH groups, and promoted the growth of hydroxyapatite.


Assuntos
Materiais Biocompatíveis/química , Radical Hidroxila/química , Lasers , Titânio/química , Cristalização , Durapatita/química , Propriedades de Superfície
12.
J Am Chem Soc ; 140(11): 3867-3870, 2018 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-29498842

RESUMO

Helical chirality of poly(quinoxaline-2,3-diyl)s bearing a boronyl pendant at the 5-position of the quinoxaline ring was induced by condensation with chiral guests such as a diol, diamine, and amino alcohol. Reversible induction of a single-handed helical structure was achieved by using less than an equimolar amount of chiral amino alcohols to the boronyl pendants. Majority-rule-effect-based chiral amplification on the polyquinoxaline main chain was demonstrated with chiral amino alcohols with low enantiomeric excess (ee). The helical macromolecular scaffold whose helicity was thus induced was utilized in palladium-catalyzed asymmetric silaboration of meso-methylenecyclopropane (up to 92% ee) by introducing (diarylphosphino)phenyl pendants at their side chains.

13.
Sci Technol Adv Mater ; 19(1): 909-916, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30636994

RESUMO

Candidate compounds for new thermoelectric and superconducting materials, which have narrow band gap and flat bands near band edges, were exhaustively searched by the high-throughput first-principles calculation from an inorganic materials database named AtomWork. We focused on PbBi2Te4 which has the similar electronic band structure and the same crystal structure with those of a pressure-induced superconductor SnBi2Se4 explored by the same data-driven approach. The PbBi2Te4 was successfully synthesized as single crystals using a melt and slow cooling method. The core level X-ray photoelectron spectroscopy analysis revealed Pb2+, Bi3+ and Te2- valence states in PbBi2Te4. The thermoelectric properties of the PbBi2Te4 sample were measured at ambient pressure and the electrical resistance was also evaluated under high pressure using a diamond anvil cell with boron-doped diamond electrodes. The resistance decreased with increasing of the pressure, and pressure-induced superconducting transitions were discovered at 2.5 K under 10 GPa. The maximum superconducting transition temperature increased up to 8.4 K at 21.7 GPa. The data-driven approach shows promising power to accelerate the discovery of new thermoelectric and superconducting materials.

14.
Angew Chem Int Ed Engl ; 57(30): 9465-9469, 2018 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-29863762

RESUMO

The palladium-catalyzed asymmetric side-chain C(α)-allylation of 2-alkylpyridines, without using an external base, was developed. The high linear selectivities and enantioselectivities were achieved using new chiral diamidophosphite monodentate ligands. Given that the reaction conditions do not require an external base, this catalyst system enabled chemoselective C(α)-allylation of 2-alkylpyridines containing α-carbonyl C-H bonds, which are more acidic than α-pyridyl C-H bonds.

15.
J Am Chem Soc ; 139(7): 2557-2560, 2017 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-28161948

RESUMO

Helically chiral poly(quinoxaline-2,3-diyl)s bearing 4-aminopyrid-3-yl pendants were synthesized as new helical-polymer-based chiral nucleophilic organocatalysts. The obtained chiral nucleophilic polymer catalysts exhibited high catalytic activity, enantioselectivity, and reusability in asymmetric Steglich rearrangement of oxazolyl carbonate to C-carboxyazlactone. The polyquinoxaline-based, helically chiral DMAP catalyst mediated intramolecular acyl transfer selectively, by contrast with known small-molecule-based chiral organocatalysts, which also mediate intermolecular acyl transfers.

16.
Proteins ; 84(5): 712-7, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26868175

RESUMO

Initiation factor 5B (IF5B) is a universally conserved translational GTPase that catalyzes ribosomal subunit joining. In eukaryotes, IF5B directly interacts via a groove in its domain IV with initiation factor 1A (IF1A), another universally conserved initiation factor, to accomplish efficient subunit joining. Here, we have determined the first structure of a crenarchaeal IF5B, which revealed that the archaea-specific region of IF5B (helix α15) binds and occludes the groove of domain IV. Therefore, archaeal IF5B cannot access IF1A in the same manner as eukaryotic IF5B. This fact suggests that different relationships between IF5B and IF1A exist in archaea and eukaryotes.


Assuntos
Aeropyrum/genética , Proteínas Arqueais/ultraestrutura , Fatores de Iniciação em Eucariotos/ultraestrutura , Aeropyrum/química , Proteínas Arqueais/química , Proteínas Arqueais/genética , Proteínas Arqueais/metabolismo , Cristalografia por Raios X , Fatores de Iniciação em Eucariotos/química , Fatores de Iniciação em Eucariotos/genética , Fatores de Iniciação em Eucariotos/metabolismo , Modelos Moleculares , Conformação Proteica
17.
Genes Cells ; 20(7): 613-24, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26033302

RESUMO

Two types of elongation factors alternate in their binding to the factor-binding center of the ribosome. Both binding events are accompanied by GTP hydrolysis and drive the translation elongation cycle. The multicopy ribosomal protein family, termed the stalk, contributes actively to the elongation process. Recent evidence indicates that the mobile C-terminal tail of archaeal stalk aP1 directly interacts with both the elongation factors aEF1A and aEF2. To investigate the functional significance of these interactions in recruitment of elongation factors to the factor-binding center of the ribosome, we substituted the archaeal stalk complex aL10•aP1 for the bL10•bL12 stalk complex in the Escherichia coli 50S subunit. The resultant hybrid ribosome accessed archaeal aEF1A and aEF2 in a manner dependent on the C-terminal tail containing the hydrophobic residues Leu103, Leu106 and Phe107. Bases G2659 and A2660 in the sarcin/ricin loop (SRL) of 23S rRNA were protected against DMS modification by both factors as was A1067 by aEF2. Mutagenesis indicated that this protection was dependent on the intact C-terminal tail of aP1. The results suggest a crucial role for the interactions between the stalk C-terminal tail and elongation factors in their recruitment to the SRL of 23S rRNA within the ribosome.


Assuntos
Fatores de Alongamento de Peptídeos/metabolismo , RNA Ribossômico 23S/metabolismo , Proteínas Ribossômicas/metabolismo , Subunidades Ribossômicas Maiores de Arqueas/metabolismo , Ricina/metabolismo , Archaea/metabolismo , Escherichia coli/metabolismo , Vetores Genéticos , Mutação , Pyrococcus horikoshii , Subunidades Ribossômicas Maiores de Arqueas/química
18.
Nucleic Acids Res ; 42(22): 14042-52, 2014 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-25428348

RESUMO

In all organisms, the large ribosomal subunit contains multiple copies of a flexible protein, the so-called 'stalk'. The C-terminal domain (CTD) of the stalk interacts directly with the translational GTPase factors, and this interaction is required for factor-dependent activity on the ribosome. Here we have determined the structure of a complex of the CTD of the archaeal stalk protein aP1 and the GDP-bound archaeal elongation factor aEF1α at 2.3 Å resolution. The structure showed that the CTD of aP1 formed a long extended α-helix, which bound to a cleft between domains 1 and 3 of aEF1α, and bridged these domains. This binding between the CTD of aP1 and the aEF1α•GDP complex was formed mainly by hydrophobic interactions. The docking analysis showed that the CTD of aP1 can bind to aEF1α•GDP located on the ribosome. An additional biochemical assay demonstrated that the CTD of aP1 also bound to the aEF1α•GTP•aminoacyl-tRNA complex. These results suggest that the CTD of aP1 interacts with aEF1α at various stages in translation. Furthermore, phylogenetic perspectives and functional analyses suggested that the eukaryotic stalk protein also interacts directly with domains 1 and 3 of eEF1α, in a manner similar to the interaction of archaeal aP1 with aEF1α.


Assuntos
Proteínas Arqueais/química , Fator 1 de Elongação de Peptídeos/química , Fosfoproteínas/química , Proteínas Ribossômicas/química , Substituição de Aminoácidos , Proteínas Arqueais/genética , Proteínas Arqueais/metabolismo , Guanosina Trifosfato/metabolismo , Modelos Moleculares , Fator 1 de Elongação de Peptídeos/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Ligação Proteica , Estrutura Terciária de Proteína , Pyrococcus horikoshii , Aminoacil-RNA de Transferência/metabolismo , Proteínas Ribossômicas/genética , Proteínas Ribossômicas/metabolismo
19.
Cryobiology ; 70(2): 208-10, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25661659

RESUMO

Oomyceteous snow molds, Pythium species, were reported to be less tolerant to chilling and freezing temperatures than other snow mold taxa. However, Pythium species are often found to be pathogenic on mosses in Polar Regions. We investigated the frost resistance of Pythium species from Temperate (Hokkaido, Japan) and Subantarctic Regions. Free mycelia and hyphal swellings, structures for survival, of Pythium iwayamai and Pythium paddicum lost viability within freeze-thaw 3 cycles; however, mycelia in host plants survived the treatment. It was reported that fungi in permafrost are characterized both by the presence of natural cryoprotectants in these ecotopes and by the ability to utilize their inherent mechanisms of protection. It is conceivable that plant substrates or derivatives thereof are natural cryoprotectants, enabling them to provide advantageous conditions to microorganisms under freezing conditions. Our results are the first to experimentally support this hypothesis.


Assuntos
Adaptação Fisiológica/fisiologia , Crioprotetores/metabolismo , Congelamento/efeitos adversos , Pythium/fisiologia , Sobrevivência Celular , Temperatura Baixa , Plantas
20.
Chemistry ; 20(41): 13127-31, 2014 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-25155882

RESUMO

Heteroatom-directed C-H borylation of cyclopropanes and cyclobutanes was achieved with silica-supported monophosphane-Ir catalysts. Borylation occurred at the C-H bonds located γ to the directing N or O atoms with exceptional cis stereoselectivity relative to the directing groups. This protocol was applied to the borylation of a tertiary C-H bond of a ring-fused cyclopropane.


Assuntos
Ciclobutanos/química , Ciclopropanos/química , Irídio/química , Fosfinas/química , Dióxido de Silício/química , Carbono/química , Catálise , Cristalografia por Raios X , Hidrogênio/química , Conformação Molecular , Estereoisomerismo
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