Search results for " membrana"
showing 10 items of 75 documents
Membrane insertion and topology of the TRanslocating chain-Associating Membrane protein (TRAM)
2011
The translocating chain-associating membrane protein (TRAM) is a glycoprotein involved in the translocation of secreted proteins into the endoplasmic reticulum (ER) lumen and in the insertion of integral membrane proteins into the lipid bilayer. As a major step toward elucidating the structure of the functional ER translocation/insertion machinery, we have characterized the membrane integration mechanism and the transmembrane topology of TRAM using two approaches: photocross-linking and truncated C-terminal reporter tag fusions. Our data indicate that TRAM is recognized by the signal recognition particle and translocon components, and suggest a membrane topology with eight transmembrane seg…
Influence of proline residues in transmembrane helix packing
2003
Integral membrane proteins often contain proline residues in their alpha-helical transmembrane (TM) fragments, which may strongly influence their folding and association. Pro-scanning mutagenesis of the helical domain of glycophorin A (GpA) showed that replacement of the residues located at the center abrogates helix packing while substitution of the residues forming the ending helical turns allows dimer formation. Synthetic TM peptides revealed that a point mutation of one of the residues of the dimerization motif (L75P) located at the N-terminal helical turn of the GpA TM fragment, adopts a secondary structure and oligomeric state similar to the wild-type sequence in detergents. In additi…
BB0172, a Borrelia burgdorferi Outer Membrane Protein That Binds Integrin Α3Β1
2013
ABSTRACT Lyme disease is a multisystemic disorder caused by Borrelia burgdorferi infection. Upon infection, some B. burgdorferi genes are upregulated, including members of the microbial surface components recognizing adhesive matrix molecule (MSCRAMM) protein family, which facilitate B. burgdorferi adherence to extracellular matrix components of the host. Comparative genome analysis has revealed a new family of B. burgdorferi proteins containing the von Willebrand factor A (vWFA) domain. In the present study, we characterized the expression and membrane association of the vWFA domain-containing protein BB0172 by using in vitro transcription/translation systems in the presence of microsomal …
Influence of the C-terminus of the glycophorin A transmembrane fragment on the dimerization process
2000
The monomer-dimer equilibrium of the glycophorin A (GpA) transmembrane (TM) fragment has been used as a model system to investigate the amino acid sequence requirements that permit an appropriate helix-helix packing in a membrane‐mimetic environment. In particular, we have focused on a region of the helix where no crucial residues for packing have been yet reported. Various deletion and replacement mutants in the C‐terminal region of the TM fragment showed that the distance between the dimerization motif and the flanking charged residues from the cytoplasmic side of the protein is important for helix packing. Furthermore, selected GpA mutants have been used to illustrate the rearrangement o…
RNA-binding properties and membrane insertion of Melon necrotic spot virus (MNSV) double gene block movement proteins
2006
AbstractAdvances in structural and biochemical properties of carmovirus movement proteins (MPs) have only been obtained in p7 and p9 from Carnation mottle virus (CarMV). Alignment of carmovirus MPs revealed a low conservation of amino acid identity but interestingly, similarity was elevated in regions associated with the functional secondary structure elements reported for CarMV which were conserved in all studied proteins. Nevertheless, some differential features in relation with CarMV MPs were identified in those from Melon necrotic virus (MNSV) (p7A and p7B). p7A was a soluble non-sequence specific RNA-binding protein, but unlike CarMV p7, its central region alone could not account for t…
Estudio de anticuerpos frente antígenos de membrana neuronal en síndromes neurológicos con hiperexcitabilidad motora
2017
El Síndrome Opsoclonus-Mioclonus (SOM) y la Neuromiotonía (NMT) son enfermedades neurológicas, caracterizadas por movimientos involuntarios, que en ocasiones presentan asociaciones paraneoplásicas(neuroblastoma en niños y timoma, respectivamente). Estas enfermedades se han relacionado con procesos autoinmunes. A pesar los esfuerzos de numerosos grupos de investigación por determinar los antígenos responsables de estas enfermedades, todavía son desconocidos. Empleando técnicas de inmunoprecipitación con diferentes sustratos y expresando las proteínas identificadas en células no neurales, tratamos de identificar en estas enfermedades nuevos antígenos de superficie, accesibles para los anticue…
Diepoxyrollin and Diepomuricanin B: Two New Diepoxyacetogenins from Rollinia membranacea Seeds
1997
Diepoxyrollin (1) and diepomuricanin B (2), two new Annonaceous acetogenins were isolated from the cytotoxic MeOH extract of the seeds of Colombian Rollinia membranacea. Five others known acetogenins were also isolated, dieporeticanin 1, dieporeticanin 2, diepomuricanin A, rollinone, and sylvaticin. Their structures were elucidated on the basis of spectral data. Compounds 1 and 2 belong to the rare type of diepoxyacetogenins, which are probably precursors of the mono-tetrahydrofuran acetogenins.
Physyological role of t-PMET in erythrocytes redox homeostasis: influence of flavonoids
2013
PHYSYOLOGICAL ROLE OF t-PMET IN ERYTHROCYTES REDOX HOMEOSTASIS:INFLUENCE OF FLAVONOIDS D. Di Majo1, M. La Guardia2, M. Crescimanno1, C. Flandina1, G. Leto1, M. Giammanco1 1Unità Didattico Scientifica di Fisiologia e Farmacologia, Dip. DIGSPO, Università di Palermo; 2Dip. STEBICEF, Università degli Studi di Palermo. Corresponding author: Danila Di Majo, Unità Didattico Scientifica di Fisiologia e Farmacologia, Dip. DIGSPO,Università degli Studi di Palermo. e-mail. danila.dimajo@unipa.it, phone +390916236405 Background In the last decade the trans-Plasma Membrane Electron Transport (t-PMET) has been subject to more research. Ever growing evidence has demonstrated that t-PMET occurs in all typ…
Biogenesis and roles of Lacticaseibacillus casei BL23 membrane vesicles
2023
Gram-positive bacteria of the species Lacticaseibacillus casei (formerly known as Lactobacillus casei) are fermentative bacilli found in dairy products that are known for their anti-inflammatory properties and beneficial effects against pathogens. Like all living organisms, L. casei produces nanostructures of 20 to 400 nm in diameter bounded by a lipid membrane called membrane vesicles (MVs). MVs have been shown to contain various cellular constituents and exert multiple functions. However, despite the growing interest in Gram-positive MVs over the past 10 years, the mechanisms of biogenesis and the roles played by these vesicles remain poorly characterized. In this context, the objectives …
Folding and insertion of transmembrane helices at the ER
2021
In eukaryotic cells, the endoplasmic reticulum (ER) is the entry point for newly synthesized proteins that are subsequently distributed to organelles of the endomembrane system. Some of these proteins are completely translocated into the lumen of the ER while others integrate stretches of amino acids into the greasy 30 Å wide interior of the ER membrane bilayer. It is generally accepted that to exist in this non-aqueous environment the majority of membrane integrated amino acids are primarily non-polar/hydrophobic and adopt an α-helical conformation. These stretches are typically around 20 amino acids long and are known as transmembrane (TM) helices. In this review, we will consider how tra…