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1.
Opt Express ; 28(6): 8211-8222, 2020 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-32225450

RESUMO

Major reshaping of electromagnetic MM-wave beams transmitted at resonant frequencies through high-quality multilayer structures is demonstrated. Beam reshaping emerges due to efficient excitation of intrinsic quasi-optical modes with complex spatial profiles by an incident beam. This leads to a significant increase of width and distortion of shape of transmitted beams, which grow with increasing likelihood of excitation of higher-order modes. The beam shape is extremely sensitive to imperfections of real structures and can become complex and asymmetric even at the normal-angle transmission of symmetric incident beams. The effect is of importance for the resonant MM-wave and THz spectroscopy of low-loss dielectric materials.

2.
Voen Med Zh ; 337(2): 31-5, 2016 Feb.
Artigo em Russo | MEDLINE | ID: mdl-27263209

RESUMO

Palliative treatment of obstructive jaundice with the help of biliary endoprosthesis due to the possible complication of post-intervention in the form of insolvency stent deformation or dislocation. The study features in the postoperative period of the main bile duct endoprosthesis about their two-component unit, described the syndrome of the closed space of the bile ducts. On the basis of observation of 14 patients with the given anatomical feature of endoscopic, who were underwent stenting, was assessed frequency of the syndrome and possibilities of its prevention. Interstenosis space expansion of the main bile duct can be a reason for local cholangitis. For the prevention of cholangitis, it should be carried out a separate drainage of interstenosis space with the help of endoprosthesis or by proximal supra-stenotic extension of two or more stents.


Assuntos
Ductos Biliares/cirurgia , Colangite , Icterícia Obstrutiva , Complicações Pós-Operatórias , Falha de Prótese/efeitos adversos , Stents/efeitos adversos , Doença Aguda , Adolescente , Adulto , Colangite/diagnóstico por imagem , Colangite/etiologia , Colangite/terapia , Humanos , Icterícia Obstrutiva/diagnóstico por imagem , Icterícia Obstrutiva/etiologia , Icterícia Obstrutiva/terapia , Masculino , Complicações Pós-Operatórias/diagnóstico por imagem , Complicações Pós-Operatórias/terapia , Radiografia
3.
Gig Sanit ; 95(10): 969-73, 2016.
Artigo em Russo | MEDLINE | ID: mdl-29431345

RESUMO

There are presented results of the cytome analysis of epithelium of buccal mucosa in 167 children aged of 5-7 years, permanently residing in the city of Magnitogorsk and visiting municipal kindergartens. Frequencies of the main indices of genotoxic and toxic effects were: cells with micronuclei - 0.29±0.04 %, with protrusions ofnuclei - 1.47±0.17 %, with double nuclei -1.96±0.13 %, with two nuclei - 3,28±0,16 %, with perinuclear vacuole - 9.66±0.86 %, with pycnosis of nucleus - 4.60±0.31 per 1000 cells, with karyorrhexis - 0.86±0.15per 1000 cells, with lysis of nucleus - 54.34±3.90 per 1000 cells, the condensed chromatin cells - 10.59±1.35 per 1000 cells. Most of these indices didn't differ from the same detected earlier in buccal epithelial cells from children of the same age in Moscow, except cells with perinuclear vacuole, which frequency in Moscow cohort was twice higher. Frequencies of cells with these anomalies were associated with the content of 19 out of 326 revealed components of contamination of the total-winter snow samples, taken on the territories of the kindergartens, which were visited by examined children. There was shown lack of differences from basic values of main indices previously establishedfor the children of the same age in Moscow, with the exception of cells with perinuclear vacuole, the rate of which in Moscow was twice higher. There were revealed confounding factors associated with test indices: gender of the child, the annual number of acute respiratory diseases, health group, income per one person in family, alcohol intake by parents.


Assuntos
Exposição Ambiental , Testes para Micronúcleos , Mucosa Bucal/patologia , Poluição da Água , Criança , Pré-Escolar , Exposição Ambiental/efeitos adversos , Exposição Ambiental/análise , Feminino , Disparidades nos Níveis de Saúde , Humanos , Masculino , Testes para Micronúcleos/métodos , Testes para Micronúcleos/estatística & dados numéricos , Medição de Risco/métodos , Medição de Risco/estatística & dados numéricos , Fatores de Risco , Federação Russa/epidemiologia , Neve , Poluição da Água/efeitos adversos , Poluição da Água/análise
4.
Eksp Klin Gastroenterol ; (10): 75-79, 2016.
Artigo em Inglês, Russo | MEDLINE | ID: mdl-29889378

RESUMO

The aim of this study was to study meaning of bile ducts angulation in postcholecystectomical syndrome developing. MATERIALS AND METHODS: There were 27 patients to be followed-up, 15 of them were performed long-term multi-stent placement in order to pursue bile ducts angulation to be liquidate and angles. After that control estimation was having versus 12 patients of control group. RESULTS: Author have seen diminish average amount of angles, their increased and accelerate of evacuation contrast speed into duodenum. That all have correlate with severe of postcholecystectomical syndrome and positive dynamic. CONCLUSION: The bile ducts angulation have meaning in postcholecystectomical syndrome developing and long-term multi-stent placement is effective way of its treatment.


Assuntos
Ductos Biliares , Síndrome Pós-Colecistectomia , Stents , Ductos Biliares/diagnóstico por imagem , Ductos Biliares/cirurgia , Feminino , Seguimentos , Humanos , Masculino , Síndrome Pós-Colecistectomia/diagnóstico por imagem , Síndrome Pós-Colecistectomia/cirurgia
5.
Rep Prog Phys ; 77(4): 046502, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24695004

RESUMO

Fe-based superconductors bridge a gap between MgB2 and the cuprate high temperature superconductors as they exhibit multiband character and transition temperatures up to around 55 K. Investigating Fe-based superconductors thus promises answers to fundamental questions concerning the Cooper pairing mechanism, competition between magnetic and superconducting phases, and a wide variety of electronic correlation effects. The question addressed in this review is, however, is this new class of superconductors also a promising candidate for technical applications? Superconducting film-based technologies range from high-current and high-field applications for energy production and storage to sensor development for communication and security issues and have to meet relevant needs of today's society and that of the future. In this review we will highlight and discuss selected key issues for Fe-based superconducting thin film applications. We initially focus our discussion on the understanding of physical properties and actual problems in film fabrication based on a comparison of different observations made in the last few years. Subsequently we address the potential for technological applications according to the current situation.

6.
Mol Gen Mikrobiol Virusol ; (2): 13-6, 2013.
Artigo em Russo | MEDLINE | ID: mdl-24003507

RESUMO

TNF is an inflammatory cytokine that involved in pathogenesis of different malignancies. Promoter single nucleotide polymorphism -238(G/A)TNF (rs361525) is investigated for the detection of susceptibility to the infectious, autoimmune and oncological diseases. The goal of the study was to investigate the association of-238(G/A)TNF polymorphism (rs361525) with breast cancer (BC) prognosis. -238(G/A) TNF allelic variants were detected by PCR-RFLP. We failed to reveal the genotype distributions disparity among groups with different stages of the disease, ER, PR or Her2/neu positive versus negative status. The AG genotype frequency was about 10% and there were no BC patients with AA genotype in all separated groups. However the overall survival was significantly lower for AG then for GG carriers with II stage or ER-positive BC. Our data suggest that -238(G/A)TNF polymorphism perhaps is not involved in the initiation of malignancies but it is a substantial factor of BC prognosis.


Assuntos
Biomarcadores Tumorais/metabolismo , Neoplasias da Mama/genética , Polimorfismo de Nucleotídeo Único , Fatores de Necrose Tumoral/genética , Adulto , Idoso , Alelos , Biomarcadores Tumorais/genética , Neoplasias da Mama/diagnóstico , Estudos de Casos e Controles , Feminino , Frequência do Gene , Estudos de Associação Genética , Genótipo , Humanos , Pessoa de Meia-Idade , Prognóstico , Regiões Promotoras Genéticas
7.
Gig Sanit ; (1): 76-80, 2013.
Artigo em Russo | MEDLINE | ID: mdl-23805702

RESUMO

Promising application of nanoparticles and nanomaterials is the creation of sanitary hygienic means of new generation used for disinfection of water and indoor surfaces of mass use, furniture, sanitary technical equipment by virtue of modifying traditional materials to bring them effective biocidal properties, and for the development of methods in vitro for assessment their toxicity In this paper the possibility of the use various forms of silver, copper and aluminum as disinfectant for bacterial test organisms in the aquatic environment and assess their toxicity on biological models of continuous culture of BGM cells (a stable line of African green monkey kidney cells) and HEp-2 (Human epithelial type 2 (HEp-2) cells, derived from a human laryngeal carcinoma) is considered.


Assuntos
Alumínio/química , Cobre/química , Nanopartículas Metálicas/toxicidade , Prata/química , Animais , Linhagem Celular , Linhagem Celular Tumoral , Chlorocebus aethiops , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Humanos , Rim/citologia , Rim/efeitos dos fármacos , Rim/metabolismo , Nanopartículas Metálicas/química
8.
Clin Exp Immunol ; 160(3): 305-17, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20345978

RESUMO

CD147 is a widely expressed plasma membrane protein that has been implicated in a variety of physiological and pathological activities. It is best known for its ability to function as extracellular matrix metalloproteinase inducer (hence the other name for this protein, EMMPRIN), but has also been shown to regulate lymphocyte responsiveness, monocarboxylate transporter expression and spermatogenesis. These functions reflect multiple interacting partners of CD147. Among these CD147-interacting proteins cyclophilins represent a particularly interesting class, both in terms of structural considerations and potential medical implications. CD147 has been shown to function as a signalling receptor for extracellular cyclophilins A and B and to mediate chemotactic activity of cyclophilins towards a variety of immune cells. Recent studies using in vitro and in vivo models have demonstrated a role for cyclophilin-CD147 interactions in the regulation of inflammatory responses in a number of diseases, including acute lung inflammation, rheumatoid arthritis and cardiovascular disease. Agents targeting either CD147 or cyclophilin activity showed significant anti-inflammatory effects in experimental models, suggesting CD147-cyclophilin interactions may be a good target for new anti-inflammatory therapeutics. Here, we review the recent literature on different aspects of cyclophilin-CD147 interactions and their role in inflammatory diseases.


Assuntos
Lesão Pulmonar Aguda/tratamento farmacológico , Anti-Inflamatórios/uso terapêutico , Artrite Reumatoide/tratamento farmacológico , Basigina/imunologia , Doenças Cardiovasculares/tratamento farmacológico , Ciclofilina A/imunologia , Ciclofilinas/imunologia , Lesão Pulmonar Aguda/imunologia , Lesão Pulmonar Aguda/metabolismo , Animais , Artrite Reumatoide/imunologia , Artrite Reumatoide/metabolismo , Basigina/metabolismo , Doenças Cardiovasculares/imunologia , Doenças Cardiovasculares/metabolismo , Ciclofilina A/metabolismo , Ciclofilinas/metabolismo , Modelos Animais de Doenças , Sistemas de Liberação de Medicamentos/métodos , Feminino , Humanos , Inflamação/tratamento farmacológico , Inflamação/imunologia , Inflamação/metabolismo , Masculino , Transportadores de Ácidos Monocarboxílicos/imunologia , Transportadores de Ácidos Monocarboxílicos/metabolismo
9.
Phys Rev Lett ; 98(11): 117002, 2007 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-17501077

RESUMO

A theoretical model for how Bloch walls occurring in in-plane magnetized ferrite garnet films can serve as efficient magnetic micromanipulators is presented. As an example, the walls' interaction with Abrikosov vortices in a superconductor in close contact with a garnet film is analyzed within the London approximation. The model explains how vortices are attracted to such walls, and excellent quantitative agreement is obtained for the resulting peaked flux profile determined experimentally in NbSe(2) using high-resolution magneto-optical imaging of vortices. In particular, this model, when generalized to include charged magnetic walls, explains the counterintuitive attraction observed between vortices and a Bloch wall of opposite polarity.

10.
Parasitology ; 133(Pt 5): 537-46, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16834819

RESUMO

A flagellate isolated from the intestinal tract of a reduviid bug Ricolla simillima (Heteroptera) in Costa Rica was found to represent a new trypanosomatid species by the phylogenetic analysis of small subunit ribosomal RNA (SSU rRNA), glyceraldehyde phosphate dehydrogenase (GAPDH) and large subunit of RNA polymerase II (RPOIILS) genes. The phylogenetic position of this trypanosomatid, together with its typical promastigote morphology and the host identity, allowed its classification as a species that belongs to the polyphyletic genus Leptomonas. Interestingly, the new species was revealed as a member of the novel phylogenetic clade representing the closest known relative of Leishmania. With the new species used as an outgroup to root the Leishmania RPOIILS phylogenetic tree, the lineage of the Neotropical species L. enriettii was found to branch off early, and was followed by a deep split between the Old World and the remaining New World species. This tree topology supports the hypothesis that the initial transition to dixenous parasitism in this group pre-dated the continental split and that afterwards the Neotropical and the Old World groups evolved largely independently.


Assuntos
Trypanosomatina/classificação , Animais , RNA Polimerases Dirigidas por DNA/genética , Gliceraldeído-3-Fosfato Desidrogenases/genética , Heterópteros/parasitologia , Interações Hospedeiro-Parasita , Intestinos/parasitologia , Leishmania/classificação , Leishmania/isolamento & purificação , Leishmania/fisiologia , Filogenia , Proteínas de Protozoários/genética , RNA de Protozoário/genética , RNA Ribossômico , Especificidade da Espécie , Trypanosomatina/isolamento & purificação , Trypanosomatina/fisiologia
11.
Bull Exp Biol Med ; 139(1): 52-5, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16142275

RESUMO

We studied mutagenic, embryotoxic, and teratogenic properties of calcium ketopantoyl aminobutyrate, a preparation proposed as a new drug. Long-term oral administration of calcium ketopantoyl aminobutyrate produced no mutagenic, embryotoxic, and teratogenic effects.


Assuntos
Aminobutiratos/toxicidade , Nootrópicos/toxicidade , Ácido Pantotênico/análogos & derivados , Anormalidades Induzidas por Medicamentos , Animais , Embrião de Mamíferos/efeitos dos fármacos , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Mutagênese , Testes de Mutagenicidade , Mutagênicos/toxicidade , Mutação , Ácido Pantotênico/toxicidade , Gravidez
12.
Biochem Biophys Res Commun ; 288(4): 786-8, 2001 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-11688976

RESUMO

Cyclophilins A and B (CyPA and CyPB) are cyclosporin A binding proteins that can be secreted in response to inflammatory stimuli. We recently identified CD147 as a cell-surface receptor for CyPA and demonstrated that CD147 is an essential component in the CyPA-initiated signaling cascade that culminates in ERK activation and chemotaxis. Here we demonstrate that CD147 also serves as a receptor for CyPB. CyPB induced Ca(2+) flux and chemotaxis of CD147-transfected, but not control, CHO cells, and the chemotactic response of primary human neutrophils to CyPB was blocked by antibodies to CD147. These results suggest that CD147 serves as a receptor for extracellular cyclophilins.


Assuntos
Antígenos CD , Antígenos de Neoplasias , Antígenos de Superfície , Proteínas Aviárias , Proteínas Sanguíneas , Sinalização do Cálcio/efeitos dos fármacos , Ciclofilinas/farmacologia , Glicoproteínas de Membrana/metabolismo , Animais , Anticorpos/imunologia , Anticorpos/farmacologia , Basigina , Células CHO , Células Cultivadas , Quimiotaxia/efeitos dos fármacos , Cricetinae , Ciclofilina A/farmacologia , Ativação Enzimática/efeitos dos fármacos , Humanos , Glicoproteínas de Membrana/antagonistas & inibidores , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/imunologia , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Infiltração de Neutrófilos/efeitos dos fármacos , Neutrófilos/efeitos dos fármacos , Neutrófilos/enzimologia , Neutrófilos/metabolismo , Peptidilprolil Isomerase , Fosforilação/efeitos dos fármacos
13.
Proc Natl Acad Sci U S A ; 98(11): 6360-5, 2001 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-11353871

RESUMO

Cyclophilin A (CyPA) is specifically incorporated into the virions of HIV-1 and has been shown to enhance significantly an early step of cellular HIV-1 infection. Our preliminary studies implicated CD147 as a receptor for extracellular CyPA. Here, we demonstrate a role for CyPA-CD147 interaction during the early steps of HIV-1 infection. Expression of human CD147 increased infection by HIV-1 under one-cycle conditions. However, susceptibility to infection by viruses lacking CyPA (simian immunodeficiency virus or HIV-1 produced in the presence of cyclosporin A) was unaffected by CD147. Virus-associated CyPA coimmunoprecipitated with CD147 from infected cells. Antibody to CD147 inhibited HIV-1 entry as evidenced by the delay in translocation of the HIV-1 core proteins from the membrane and inhibition of viral reverse transcription. Viruses whose replication did not require CyPA (SIV or mutant HIV-1) were resistant to the inhibitory effect of anti-CD147 antibody. These results suggest that HIV-1 entry depends on an interaction between virus-associated CyPA and CD147 on a target cell.


Assuntos
Antígenos CD , Antígenos de Neoplasias , Antígenos de Superfície , Proteínas Aviárias , Proteínas Sanguíneas , Ciclofilina A/metabolismo , HIV-1/fisiologia , Glicoproteínas de Membrana/metabolismo , Animais , Anticorpos Monoclonais/metabolismo , Basigina , Células CHO , Cricetinae , HIV-1/metabolismo , Humanos , Glicoproteínas de Membrana/genética
14.
Chemosphere ; 43(4-7): 999-1004, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11372894

RESUMO

Three groups of women (aged 20-40 years) exposed to different levels of dioxins were studied in Chapaevsk town: 15 women working at the chemical fertilizer plant where occupational exposure to dioxins is possible; 16 women without dioxins occupational exposure, but living as far as 1-3 km from the plant; 14 women without dioxins occupational exposure and living as far as 5-8 km from the plant. No personal correlation related to dioxins exposure was found by chromosome aberrations (CA) in peripheral blood lymphocytes, micronuclei (MN) and nuclear anomalies in buccal mucosa cells. There were no significant differences between the groups in CA and MN. Karyopyknosis and karyorrhexis were significantly increased in the highest exposed group.


Assuntos
Aberrações Cromossômicas , Dioxinas/efeitos adversos , Exposição Ocupacional , Adulto , Exposição Ambiental , Feminino , Fertilizantes , Humanos , Indústrias , Mucosa Bucal
15.
Phys Rev E Stat Nonlin Soft Matter Phys ; 63(4 Pt 2): 046501, 2001 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-11308960

RESUMO

An alternative approach has been developed to the numerical synthesis of ion-beam focusing systems that prepare the dense laminar ion beams with the required profile of the ion trajectories. Conventionally an ill-posed synthesis problem arises in such cases, and only low-density beams with no magnetic field are treated. Instead, we compute both the electric and magnetic fields by considering two well-posed problems, the first for the equivalent potential Q and the second for the electric potential U. An analytical solution for Q for the specific case of an axial system has been found and a self-consistent method of satisfying the axial boundary conditions for Poisson's equation in U is described. It is shown that the beam can be focused while preserving its laminar structure and the required profile when applying various superpositions of both the electric and magnetic fields.

16.
J Eukaryot Microbiol ; 48(2): 161-9, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-12095103

RESUMO

With the aim of further investigating phylogenetic relationships in insect trypanosomatids, we have determined the sequences of small subunit rRNA genes from ten isolates, which were originally classified as Leptomonas, Blastocrithidia, and Wallaceina based on their morphology in the hosts. The inferred maximum likelihood, parsimony, and distance trees indicate that the Leptomonas and Blastocrithidia are polyphyletic, and confirm the polyphyly of Herpetomonas and Crithidia. Blastocrithidia triatoma and Leptomonas collosoma were among the earliest branching lineages among the insect trypanosomatids, while most other isolates were found within a closely related terminal clade, which also included Crithidia fasciculata. This analysis has clearly demonstrated that the morphological classification system of insect trypanosomatids does not always reflect their genetic affinities warranting its revision in the future.


Assuntos
Genes de RNAr , Variação Genética , Filogenia , Trypanosomatina/classificação , Animais , Genes de Protozoários , Funções Verossimilhança , Trypanosomatina/citologia , Trypanosomatina/genética
17.
Folia Parasitol (Praha) ; 47(1): 1-5, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10833008

RESUMO

Phylogenetic relationships within the suborder Trypanosomatina were inferred from the kinetoplast DNA minicircle conserved region sequences. Trees built using distance-matrix (Neighbor-Joining) and maximum parsimony methods showed that the minicircle conserved regions (CRs) provide a sensitive and specific molecular marker suitable for phylogenetic analyses of subspecies and strains of trypanosomatid flagellates, as testified by the subdivision of the genus Leishmania into the subgenera Leishmania. Viannia and Sauroleishmania. However, since Phytomonas and monogenetic parasites of insects represent the earliest diverging groups, the CRs do not seem to be useful for inference of relationships among major lineages of the order Kinetoplastida.


Assuntos
DNA de Cinetoplasto/genética , Genes de Protozoários , Trypanosomatina/classificação , Animais , Filogenia , Trypanosomatina/genética
18.
J Biomol Struct Dyn ; 17(4): 687-95, 2000 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-10698106

RESUMO

Intramolecular compact structures formed by high molecular weight circular superhelical DNA molecules due to interaction with synthetic oligopeptide trivaline (1) were studied by atomic force and electron microscopy. Three DNA preparations were used: plasmids pTbol, pRX10 and cosmid 27,877, with sizes 6,120 bp, 10,500 bp and 44,890 bp respectively. Plasmid pTbo1 and pRX10 preparations along with monomers contained significant amount of dimers and trimers. Main structures in all preparations observed were compact particles, which coincide in their appearance and compaction coefficient (3,5-3,7) with triple rings described earlier. The size and structure characteristics of triple rings and other compact particles on atomic force images in general coincide with those obtained by EM (2). AFM (3) images allow to get additional information about the ultrastructural organization and arrangement of DNA fibers within the compact structures. Along with triple rings in pTbol and pRX10-TVP complexes significant amount of compact structures were observed having the shape of two or three compact rings attached to each other by a region of compact fibre. Basing on the data of contour length measurements and the shape of the particles it was concluded that these structures were formed due to compaction of dimeric and trimeric circular DNA molecules. Structures consisting of several attached to each other triple rings were not found for pTbol, pRX10 monomers or cosmid preparations--TVP complexes where only single triple rings were observed. The conclusion is made that initiation of compact fibre formation within the circular molecules depends on the primary structure and for dimeric or trimeric circular molecules two or three compaction initiation points are present, located in each monomer unit within one circular DNA molecule. The nucleotide sequence dependent compaction mechanism providing independent compaction of portions of one circular molecule can be of interest for understanding of DNA compaction processes in vivo.


Assuntos
DNA Super-Helicoidal/ultraestrutura , Oligopeptídeos/química , Valina/química , Cosmídeos , DNA Super-Helicoidal/química , Humanos , Microscopia de Força Atômica , Microscopia Eletrônica
19.
Eur J Biochem ; 265(1): 160-70, 1999 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-10491170

RESUMO

Geranylgeranylation is a post-translational modification of Rab GTPases that enables them to associate reversibly with intracellular membranes. Geranylgeranylation of Rab proteins is critical for their activity in controlling intracellular membrane transport. According to the currently accepted model for their action, newly synthesized Rab proteins are recruited by Rab escort protein (REP) and are presented to the Rab geranylgeranyl transferase (RabGGTase) which covalentely modifies the Rab protein with two geranylgeranyl moieties. After prenylation, the Rab protein remains in complex with REP and is delivered to the target membrane by the latter. In this work, we show that RabGGTase can form a stable complex with Rab7-REP in the absence of its lipid substrate geranylgeranyl pyrophosphate. In order to characterize this interaction, we developed three fluorescence assays reporting on the interaction of RabGGTase with the Rab7-REP complex. For this interaction we determined a Kd value of about 120 nM. Association of RabGGTase with the Rab7-REP complex occurs with a rate constant of approximately 108 M-1 x s-1. We demonstrate that the state of the nucleotide bound to Rab7 does not influence the affinity of RabGGTase for the Rab7-REP-1 complex. Finally, we address the issue of substrate specificity of RabGGTase. Titration experiments demonstrate that, in contrast with farnesyl transferase, RabGGTase does not recognize a defined C-terminal sequence motif. Experiments using Rab7 mutants in which the last 16 amino acids were either mutated or truncated revealed that the distal part of the C-terminus makes only a limited contribution to the binding affinity between RabGGTase and the Rab7-REP-1 complex. This demonstrates the functional dissimilarity between RabGGTase and geranylgeranyl transferase I and farnesyl transferase, which interact specifically with the C-terminus of their substrates. Based on these experiments, we propose that RabGGTase recognizes the overall structure arising from the association of Rab and REP and then 'scans' the flexible C-terminus to position the proximal cysteines into the active site.


Assuntos
Alquil e Aril Transferases/metabolismo , Proteínas de Transporte/metabolismo , Prenilação de Proteína , Proteínas rab de Ligação ao GTP/metabolismo , Alquil e Aril Transferases/genética , Proteínas de Transporte/genética , Cromatografia em Gel , Compostos de Dansil , Fluorometria , Guanosina Trifosfato/metabolismo , Modelos Químicos , Ligação Proteica , Proteínas Recombinantes/metabolismo , Especificidade por Substrato , Proteínas rab de Ligação ao GTP/genética , proteínas de unión al GTP Rab7
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