0000000001212341
AUTHOR
Silvia Tamborero
Viral membrane protein topology is dictated by multiple determinants in its sequence.
The targeting, insertion, and topology of membrane proteins have been extensively studied in both prokaryotes and eukaryotes. However, the mechanisms used by viral membrane proteins to generate the correct topology within cellular membranes are less well understood. Here, the effect of flanking charges and the hydrophobicity of the N-terminal hydrophobic segment on viral membrane protein topogenesis are examined systematically. Experimental data reveal that the classical topological determinants have only a minor effect on the overall topology of p9, a plant viral movement protein. Since only a few individual sequence alterations cause an inversion of p9 topology, its topological stability …
BB0172, a Borrelia burgdorferi Outer Membrane Protein That Binds Integrin Α3Β1
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 …
N-glycosylation efficiency is determined by the distance to the C-terminus and the amino acid preceding an Asn-Ser-Thr sequon
N-glycosylation is the most common and versatile protein modification. In eukaryotic cells, this modification is catalyzed cotranslationally by the enzyme oligosaccharyltransferase, which targets the β-amide of the asparagine in an Asn-Xaa-Ser/Thr consensus sequon (where Xaa is any amino acid but proline) in nascent proteins as they enter the endoplasmic reticulum. Because modification of the glycosylation acceptor site on membrane proteins occurs in a compartment-specific manner, the presence of glycosylation is used to indicate membrane protein topology. Moreover, glycosylation sites can be added to gain topological information. In this study, we explored the determinants of N-glycosylati…
Tiratricol neutralizes bacterial endotoxins and reduces lipopolysaccharide-induced TNF-alpha production in the cell.
Contains fulltext : 70610.pdf (Publisher’s version ) (Closed access) The screening of a commercially available library of compounds has proved a successful strategy for the identification of a lead compound in a drug discovery programme. Here, we analysed 880 off-patent drugs, which initially comprised the Prestwick Chemical library, as sources of bacterial endotoxin neutralizers. We identified 3,3',5-triiodo-thyroacetic acid (tiratricol) as a non-antibacterial compound that neutralizes the toxic lipopolysaccharide.
Membrane insertion and topology of the TRanslocating chain-Associating Membrane protein (TRAM)
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…
Membrane topology of gp41 and amyloid precursor protein: Interfering transmembrane interactions as potential targets for HIV and Alzheimer treatment
AbstractThe amyloid precursor protein (APP), that plays a critical role in the development of senile plaques in Alzheimer disease (AD), and the gp41 envelope protein of the human immunodeficiency virus (HIV), the causative agent of the acquired immunodeficiency syndrome (AIDS), are single-spanning type-1 transmembrane (TM) glycoproteins with the ability to form homo-oligomers. In this review we describe similarities, both in structural terms and sequence determinants of their TM and juxtamembrane regions. The TM domains are essential not only for anchoring the proteins in membranes but also have functional roles. Both TM segments contain GxxxG motifs that drive TM associations within the li…
The Tobacco mosaic virus movement protein associates with but does not integrate into biological membranes
Plant positive-strand RNA viruses require association with plant cell endomembranes for viral translation and replication, as well as for intra- and intercellular movement of the viral progeny. The membrane association and RNA binding of the Tobacco mosaic virus (TMV) movement protein (MP) are vital for orchestrating the macromolecular network required for virus movement. A previously proposed topological model suggests that TMV MP is an integral membrane protein with two putative -helical transmembrane (TM) segments. Here we tested this model using an experimental system that measured the efficiency with which natural polypeptide segments were inserted into the ER membrane under conditions…
Transmembrane but not soluble helices fold inside the ribosome tunnel
Integral membrane proteins are assembled into the ER membrane via a continuous ribosome-translocon channel. The hydrophobicity and thickness of the core of the membrane bilayer leads to the expectation that transmembrane (TM) segments minimize the cost of harbouring polar polypeptide backbones by adopting a regular pattern of hydrogen bonds to form α-helices before integration. Co-translational folding of nascent chains into an α-helical conformation in the ribosomal tunnel has been demonstrated previously, but the features governing this folding are not well understood. In particular, little is known about what features influence the propensity to acquire α-helical structure in the ribosom…