Bosentan, an endothelin-1 (ET) receptor antagonist is an important drug for the effective management of patients with pulmonary arterial hypertension. Bosentan has a rather complicated pharmacokinetics in humans involving multiple physiological components that have a profound influence on its drug disposition. Bosentan is mainly metabolized by cytochrome P450 (CYP) 3A4 and 2C9 enzymes with the involvement of multiple transporters that control its hepatic uptake and biliary excretion. The involvement of phase 2 metabolism of bosentan is a key to have an enhanced biliary excretion of the drug-related products. While bosentan exhibits high protein binding restricting the drug from extensive distribution and significant urinary excretion, bosentan induces its own metabolism by an increased expression of CYP3A4 on repeated dosing. Due to the above properties, bosentan has the potential to display drug-drug interaction with the co-administered drugs, either being a perpetrator or a victim. The intent of this review is manifold: a) to summarize the physiological role of CYP enzymes and hepatic-biliary transporters; b) to discuss the mechanism(s) involved in the purported liver injury caused by bosentan; c) to tabulate the numerous clinical drug-drug interaction studies involving the physiological interplay with CYP and/or transporters; d) to provide some perspectives on dosing strategy of bosentan.

• MeSH
• asparagin chemie   metabolismus   MeSH
• gating iontového kanálu fyziologie   MeSH
• glykosylace MeSH
• lidé MeSH
• podjednotky proteinů MeSH
• polysacharidy chemie   metabolismus   MeSH
• vápník chemie   metabolismus   MeSH
• vápníkové kanály - typ L chemie   metabolismus   MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• asparagin MeSH
• L-type calcium channel alpha(1C) MeSH Prohlížeč
• podjednotky proteinů MeSH
• polysacharidy MeSH
• vápník MeSH
• vápníkové kanály - typ L MeSH

PURPOSE: Liddle syndrome is a hereditary form of arterial hypertension caused by mutations in the genes coding of the epithelial sodium channel - SCNN1A, SCNN1B and SCNN1G. It is characterised by early onset of hypertension and variable biochemical features such as hypokalaemia and low plasma concentrations of renin and aldosterone. Phenotypic variability is large and, therefore, LS is probably underdiagnosed. Our objective was to examine a family suspected from Liddle syndrome including genetic testing and evaluate clinical and biochemical features of affected family members. MATERIALS AND METHODS: Thirteen probands from the Czech family, related by blood, underwent physical examination, laboratory tests, and genetic testing. Alleles of SCNN1B and SCNN1G genes were examined by PCR amplification and Sanger sequencing of amplicons. RESULTS: We identified a novel mutation in the β-subunit of an epithelial sodium channel coded by the SCNN1B gene, causing the nonsense mutation in the protein sequence p.Tyr604*. This mutation was detected in 7 members of the family. The mutation carriers differed in the severity of hypertension and hypokalaemia which appeared only after diuretics in most of them; low aldosterone level (< 0.12 nmol/l) was, however, present in all. CONCLUSIONS: This finding expands the spectrum of known mutations causing Liddle syndrome. Hypoaldosteronemia was 100% sensitive sign in the mutation carriers. Low levels are observed especially in the Caucasian population reaching 96% sensitivity. Assessment of plasma aldosterone concentration is helpful for differential diagnosis of arterial hypertension. CONDENSED ABSTRACT: Liddle syndrome is a hereditary form of arterial hypertension caused by mutations in the genes encoding the epithelial sodium channel's α-, β- and γ-subunit. It is usually manifested by early onset of hypertension accompanied by low potassium and aldosterone levels. We performed a physical examination, laboratory tests and genetic screening in 13 members of a Czech family. We found a new mutation of the SCNN1B gene which encodes the β-subunit of the epithelial sodium channel. We describe the variability of each family member phenotype and point out the relevance of using aldosterone levels as a high sensitivity marker of Liddle syndrome in Caucasians.

• Klíčová slova
• Aldosterone, ENaC, Liddle syndrome, SCNN1B, hypertension, nonsense mutation, β-subunit,
• MeSH
• epiteliální sodíkový kanál genetika   MeSH
• hypertenze * genetika   MeSH
• Liddleův syndrom * genetika   MeSH
• lidé MeSH
• nesmyslný kodon * MeSH
• renin MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Česká republika MeSH
• Názvy látek
• epiteliální sodíkový kanál MeSH
• nesmyslný kodon * MeSH
• renin MeSH
• SCNN1B protein, human MeSH Prohlížeč

Biogenesis of the plant secondary cell wall involves many important aspects, such as phenolic compound deposition and often silica encrustation. Previously, we demonstrated the importance of the exocyst subunit EXO70H4 for biogenesis of the trichome secondary cell wall, namely for deposition of the autofluorescent and callose-rich cell wall layer. Here, we reveal that EXO70H4-driven cell wall biogenesis is constitutively active in the mature trichome, but also can be activated elsewhere upon pathogen attack, giving this study a broader significance with an overlap into phytopathology. To address the specificity of EXO70H4 among the EXO70 family, we complemented the exo70H4-1 mutant by 18 different Arabidopsis (Arabidopsis thaliana) EXO70 paralogs subcloned under the EXO70H4 promoter. Only EXO70H4 had the capacity to rescue the exo70H4-1 trichome phenotype. Callose deposition phenotype of exo70H4-1 mutant is caused by impaired secretion of PMR4, a callose synthase responsible for the synthesis of callose in the trichome. PMR4 colocalizes with EXO70H4 on plasma membrane microdomains that do not develop in the exo70H4-1 mutant. Using energy-dispersive x-ray microanalysis, we show that both EXO70H4- and PMR4-dependent callose deposition in the trichome are essential for cell wall silicification.

• MeSH
• Arabidopsis účinky léků   genetika   metabolismus   MeSH
• buněčná membrána účinky léků   metabolismus   MeSH
• buněčná stěna účinky léků   metabolismus   MeSH
• epidermis rostlin cytologie   účinky léků   metabolismus   MeSH
• fenotyp MeSH
• flagelin farmakologie   MeSH
• glukany MeSH
• glukosyltransferasy metabolismus   MeSH
• mutace genetika   MeSH
• oxid křemičitý metabolismus   MeSH
• podjednotky proteinů chemie   metabolismus   MeSH
• proteinové domény MeSH
• proteiny huseníčku chemie   metabolismus   MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• trichomy metabolismus   MeSH
• upregulace účinky léků   MeSH
• vezikulární transportní proteiny chemie   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 1,3-beta-glucan synthase MeSH Prohlížeč
• callose MeSH Prohlížeč
• EXO70H4 protein, Arabidopsis MeSH Prohlížeč
• flagelin MeSH
• glukany MeSH
• glukosyltransferasy MeSH
• oxid křemičitý MeSH
• PMR4 protein, Arabidopsis MeSH Prohlížeč
• podjednotky proteinů MeSH
• proteiny huseníčku MeSH
• vezikulární transportní proteiny MeSH

The passage of protons across membranes through F1Fo-ATP synthases spins their rotors and drives the synthesis of ATP. While the principle of torque generation by proton transfer is known, the mechanisms and routes of proton access and release and their evolution are not fully understood. Here, we show that the entry site and path of protons in the lumenal half channel of mitochondrial ATP synthases are largely defined by a short N-terminal α-helix of subunit-a. In Trypanosoma brucei and other Euglenozoa, the α-helix is part of another polypeptide chain that is a product of subunit-a gene fragmentation. This α-helix and other elements forming the proton pathway are widely conserved across eukaryotes and in Alphaproteobacteria, the closest extant relatives of mitochondria, but not in other bacteria. The α-helix blocks one of two proton routes found in Escherichia coli, resulting in a single proton entry site in mitochondrial and alphaproteobacterial ATP synthases. Thus, the shape of the access half channel predates eukaryotes and originated in the lineage from which mitochondria evolved by endosymbiosis.

• Klíčová slova
• Trypanosoma brucei, gene fragmentation, mitochondrial ATP synthase, proton path, proton translocation, subunit-a,
• MeSH
• adenosintrifosfát metabolismus   MeSH
• Escherichia coli genetika   metabolismus   MeSH
• Eukaryota metabolismus   MeSH
• mitochondriální protonové ATPasy * genetika   chemie   metabolismus   MeSH
• protonové ATPasy * metabolismus   MeSH
• protony MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenosintrifosfát MeSH
• mitochondriální protonové ATPasy * MeSH
• protonové ATPasy * MeSH
• protony MeSH

RNA polymerase in bacteria is a multisubunit protein complex that is essential for gene expression. We have identified a new subunit of RNA polymerase present in the high-A+T Firmicutes phylum of Gram-positive bacteria and have named it ε. Previously ε had been identified as a small protein (ω1) that copurified with RNA polymerase. We have solved the structure of ε by X-ray crystallography and show that it is not an ω subunit. Rather, ε bears remarkable similarity to the Gp2 family of phage proteins involved in the inhibition of host cell transcription following infection. Deletion of ε shows no phenotype and has no effect on the transcriptional profile of the cell. Determination of the location of ε within the assembly of RNA polymerase core by single-particle analysis suggests that it binds toward the downstream side of the DNA binding cleft. Due to the structural similarity of ε with Gp2 and the fact they bind similar regions of RNA polymerase, we hypothesize that ε may serve a role in protection from phage infection.

• MeSH
• Bacillus subtilis enzymologie   MeSH
• DNA řízené RNA-polymerasy chemie   genetika   metabolismus   MeSH
• fylogeneze MeSH
• konformace proteinů MeSH
• molekulární modely MeSH
• molekulární sekvence - údaje MeSH
• podjednotky proteinů MeSH
• regulace genové exprese enzymů MeSH
• regulace genové exprese u bakterií MeSH
• sekvence aminokyselin MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA řízené RNA-polymerasy MeSH
• podjednotky proteinů MeSH

Influenza A virus (IAV) encodes a polymerase composed of three subunits: PA, with endonuclease activity, PB1 with polymerase activity and PB2 with host RNA five-prime cap binding site. Their cooperation and stepwise activation include a process called cap-snatching, which is a crucial step in the IAV life cycle. Reproduction of IAV can be blocked by disrupting the interaction between the PB2 domain and the five-prime cap. An inhibitor of this interaction called pimodivir (VX-787) recently entered the third phase of clinical trial; however, several mutations in PB2 that cause resistance to pimodivir were observed. First major mutation, F404Y, causing resistance was identified during preclinical testing, next the mutation M431I was identified in patients during the second phase of clinical trials. The mutation H357N was identified during testing of IAV strains at Centers for Disease Control and Prevention. We set out to provide a structural and thermodynamic analysis of the interactions between cap-binding domain of PB2 wild-type and PB2 variants bearing these mutations and pimodivir. Here we present four crystal structures of PB2-WT, PB2-F404Y, PB2-M431I and PB2-H357N in complex with pimodivir. We have thermodynamically analysed all PB2 variants and proposed the effect of these mutations on thermodynamic parameters of these interactions and pimodivir resistance development. These data will contribute to understanding the effect of these missense mutations to the resistance development and help to design next generation inhibitors.

• Klíčová slova
• VX-787, antivirals, influenza A polymerase, pimodivir, resistance,
• MeSH
• krystalografie rentgenová MeSH
• kvantová teorie MeSH
• molekulární modely MeSH
• mutace genetika   MeSH
• mutantní proteiny metabolismus   MeSH
• podjednotky proteinů antagonisté a inhibitory   chemie   metabolismus   MeSH
• proteinové domény MeSH
• pyridiny chemie   farmakologie   MeSH
• pyrimidiny chemie   farmakologie   MeSH
• pyrroly chemie   farmakologie   MeSH
• RNA-dependentní RNA-polymerasa antagonisté a inhibitory   chemie   metabolismus   MeSH
• termodynamika MeSH
• virová léková rezistence účinky léků   MeSH
• virové proteiny antagonisté a inhibitory   chemie   metabolismus   MeSH
• virus chřipky A účinky léků   enzymologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• mutantní proteiny MeSH
• PB2 protein, Influenzavirus A MeSH Prohlížeč
• pimodivir MeSH Prohlížeč
• podjednotky proteinů MeSH
• pyridiny MeSH
• pyrimidiny MeSH
• pyrroly MeSH
• RNA-dependentní RNA-polymerasa MeSH
• virové proteiny MeSH

Dysfunction of mitochondrial ATPase (F1F(o)-ATP synthase) due to missense mutations in ATP6 [mtDNA (mitochondrial DNA)-encoded subunit a] is a frequent cause of severe mitochondrial encephalomyopathies. We have investigated a rare mtDNA mutation, i.e. a 2 bp deletion of TA at positions 9205 and 9206 (9205DeltaTA), which affects the STOP codon of the ATP6 gene and the cleavage site between the RNAs for ATP6 and COX3 (cytochrome c oxidase 3). The mutation was present at increasing load in a three-generation family (in blood: 16%/82%/>98%). In the affected boy with severe encephalopathy, a homoplasmic mutation was present in blood, fibroblasts and muscle. The fibroblasts from the patient showed normal aurovertin-sensitive ATPase hydrolytic activity, a 70% decrease in ATP synthesis and an 85% decrease in COX activity. ADP-stimulated respiration and the ADP-induced decrease in the mitochondrial membrane potential at state 4 were decreased by 50%. The content of subunit a was decreased 10-fold compared with other ATPase subunits, and [35S]-methionine labelling showed a 9-fold decrease in subunit a biosynthesis. The content of COX subunits 1, 4 and 6c was decreased by 30-60%. Northern Blot and quantitative real-time reverse transcription-PCR analysis further demonstrated that the primary ATP6--COX3 transcript is cleaved to the ATP6 and COX3 mRNAs 2-3-fold less efficiently. Structural studies by Blue-Native and two-dimensional electrophoresis revealed an altered pattern of COX assembly and instability of the ATPase complex, which dissociated into subcomplexes. The results indicate that the 9205DeltaTA mutation prevents the synthesis of ATPase subunit a, and causes the formation of incomplete ATPase complexes that are capable of ATP hydrolysis but not ATP synthesis. The mutation also affects the biogenesis of COX, which is present in a decreased amount in cells from affected individuals.

• MeSH
• 2D gelová elektroforéza metody   MeSH
• adenin metabolismus   MeSH
• adenosintrifosfát biosyntéza   MeSH
• adenosintrifosfatasy chemie   fyziologie   MeSH
• fibroblasty chemie   enzymologie   metabolismus   patologie   MeSH
• intracelulární membrány chemie   enzymologie   MeSH
• kultivované buňky MeSH
• kůže patologie   MeSH
• lidé MeSH
• membránové potenciály genetika   MeSH
• messenger RNA biosyntéza   MeSH
• mitochondriální DNA biosyntéza   genetika   MeSH
• mitochondriální protonové ATPasy biosyntéza   MeSH
• mitochondrie chemie   enzymologie   MeSH
• mutace genetika   MeSH
• předškolní dítě MeSH
• respirační komplex IV biosyntéza   chemie   metabolismus   fyziologie   MeSH
• sekvenční delece genetika   MeSH
• spotřeba kyslíku genetika   fyziologie   MeSH
• thymidin metabolismus   MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• předškolní dítě MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenin MeSH
• adenosintrifosfát MeSH
• adenosintrifosfatasy MeSH
• messenger RNA MeSH
• mitochondriální DNA MeSH
• mitochondriální protonové ATPasy MeSH
• MT-ATP6 protein, human MeSH Prohlížeč
• respirační komplex IV MeSH
• thymidin MeSH

Phototherapy is a standard treatment for severe neonatal jaundice to remove toxic bilirubin from the blood. Here, the wavelength-dependent photochemistry of vinylneoxanthobilirubic acid methyl ester, a simplified model of a bilirubin dipyrrinone subunit responsible for a lumirubin-like structural rearrangement, was thoroughly investigated by liquid chromatography and mass and absorption spectroscopies, with the application of a multivariate curve resolution analysis method supplemented with quantum chemical calculations. Irradiation of the model chromophore leads to reversible Z → E photoisomerization followed by reversible photocyclization to a seven-membered ring system (formed as a mixture of diastereomers). Both the isomerization processes are efficient (ΦZE ∼ ΦEZ ∼ 0.16) when irradiated in the wavelength range of 360-410 nm, whereas the E-isomer cyclization (Φc = 0.006-0.008) and cycloreversion (Φ-c = 0.002-0.004) reactions are significantly less efficient. The quantum yields of all processes were found to depend strongly on the wavelength of irradiation, especially when lower energy photons were used. Upon irradiation in the tail of the absorption bands (490 nm), both the isomers exhibit more efficient photoisomerization (ΦZE ∼ ΦEZ ∼ 0.30) and cyclization (Φc = ∼0.07). In addition, the isomeric bilirubin dipyrrinone subunits were found to possess important antioxidant activities while being substantially less toxic than bilirubin.

• MeSH
• bilirubin MeSH
• fotochemie MeSH
• fototerapie MeSH
• isomerie MeSH
• lidé MeSH
• novorozenec MeSH
• novorozenecká žloutenka * MeSH
• Check Tag
• lidé MeSH
• novorozenec MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bilirubin MeSH

All three tryptophan residues in alpha-subunit of mitochondrial processing peptidase (MPP) were subsequently substituted. While substitutions of Trp223 led to misfolded non-functional protein, mutations of Trp147 and/or Trp481 did not affect the enzyme processing activity. Thus, fluorescence properties of the mutants with fewer tryptophans were used for observation of both alpha-MPP domain translocation and visualization of conformational changes in the interdomain linker evoked by substrate. We found that in the presence of substrate the C-terminal penultimate Trp481 was approaching Trp223, which is localized at the border of N-terminal domain and interdomain linker. Also, excision of the alpha-MPP C-terminal 30 amino acid residues (DeltaC30) led to a complete loss of protein function. Even shorter deletions of the alpha-MPP C-terminus destabilized the protein slightly (DeltaC2) or dramatically (DeltaC17). It suggests that the extreme C-terminus of alpha-MPP provides mechanical support to the C-terminal domain during its extensive conformational change accompanying the substrate recognition process.

• MeSH
• fungální proteiny chemie   genetika   metabolismus   MeSH
• konformace proteinů MeSH
• metaloendopeptidasy chemie   genetika   metabolismus   MeSH
• molekulární modely MeSH
• MPP peptidasa MeSH
• podjednotky proteinů chemie   genetika   metabolismus   MeSH
• proteinové prekurzory metabolismus   MeSH
• sekvenční delece MeSH
• substituce aminokyselin MeSH
• terciární struktura proteinů MeSH
• transport proteinů MeSH
• tryptofan genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fungální proteiny MeSH
• metaloendopeptidasy MeSH
• podjednotky proteinů MeSH
• proteinové prekurzory MeSH
• tryptofan MeSH

Tryptophan fluorescence measurements were used to characterize the local dynamics of the highly conserved glycine-rich loop (GRL) of the mitochondrial processing peptidase (MPP) alpha-subunit in the presence of the substrate precursor. Reporter tryptophan residue was introduced into the GRL of the yeast alpha-MPP (Y299W) or at a proximal site (Y303W). Time-resolved and steady-state fluorescence spectroscopy demonstrated that for Trp299, the primary contact with the yeast malate dehydrogenase precursor evokes a change of the local GRL mobility. Moreover, time-resolved measurements showed that a functionless alpha-MPP with a single-residue deletion in the loop (Y303W/DeltaG292) is defective particularly in the primary contact with substrate. Thus, the GRL was proved to be part of a contact site of the enzyme specifically recognizing the substrate. Regarding the surface exposure and presence of the hydrophobic patches within the GRL, we proposed a functional analogy between the presequence recognition by the hydrophobic binding groove of the Tom20 mitochondrial import receptor and the GRL of the alpha-MPP. A molecular dynamics (MD) simulation of the MPP-substrate peptide complex model was employed to test this hypothesis. The initial positioning and conformation of the substrate peptide in the model fitting were chosen based on the analogy of its interaction with the Tom20 binding groove. MD simulation confirmed the stability of the proposed interaction and showed also a decrease in GRL flexibility in the presence of substrate, in agreement with fluorescence measurements. Moreover, conserved substrate hydrophobic residues in positions +1 and -4 to the cleavage site remain in close contact with the side chains of the GRL during the entire production part of MD simulation as stabilizing points of the hydrophobic interaction. We conclude that the GRL of the MPP alpha-subunit is the crucial evolutional outcome of the presequence recognition by MPP and represents a functional parallel with Tom20 import receptor.

• MeSH
• aminokyselinové motivy MeSH
• DNA fungální genetika   MeSH
• fluorescenční polarizace MeSH
• fluorescenční spektrometrie MeSH
• glycin chemie   MeSH
• hydrofobní a hydrofilní interakce MeSH
• katalytická doména genetika   MeSH
• kvarterní struktura proteinů MeSH
• metaloendopeptidasy chemie   genetika   metabolismus   MeSH
• molekulární modely MeSH
• molekulární sekvence - údaje MeSH
• MPP peptidasa MeSH
• mutageneze cílená MeSH
• podjednotky proteinů MeSH
• rekombinantní proteiny chemie   genetika   metabolismus   MeSH
• Saccharomyces cerevisiae - proteiny chemie   genetika   metabolismus   MeSH
• Saccharomyces cerevisiae enzymologie   genetika   MeSH
• sekvence aminokyselin MeSH
• sekvence nukleotidů MeSH
• sekvenční delece MeSH
• substituce aminokyselin MeSH
• substrátová specifita MeSH
• termodynamika MeSH
• transportní proteiny mitochondriální membrány chemie   genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA fungální MeSH
• glycin MeSH
• metaloendopeptidasy MeSH
• podjednotky proteinů MeSH
• rekombinantní proteiny MeSH
• Saccharomyces cerevisiae - proteiny MeSH
• TOM20 protein, S cerevisiae MeSH Prohlížeč
• transportní proteiny mitochondriální membrány MeSH