Search results for "Membrane topology"

Androgen-inducible gene 1 increases the ER Ca(2+) content and cell death susceptibility against oxidative stress.

2016

Androgen-induced gene 1 (AIG1) is a transmembrane protein implicated with survival (its expression level was shown to correlate with the survival of patients suffering from hepatocellular carcinoma) and Ca(2+) signaling (over-expression of AIG1 increased transcription mediated by the Ca(2+)-dependent nuclear factor of activated T cells). We aimed to shed light on this less-studied protein and investigated its tissue expression, genomic organization, intracellular localization and membrane topology as well as its effects on cell death susceptibility and the Ca(2+) content of the endoplasmic reticulum. Immunoblotting of mouse tissues demonstrated highest expression of AIG1 in the liver, lung …

Assessment of determinants affecting the dual topology of hepadnaviral large envelope proteins

2004

For functional diversity, the large (L) envelope protein of hepatitis B virus (HBV) acquires a dual transmembrane topology via co-translational membrane integration of the S region and partial post-translational translocation of the preS subdomain. Because each process requires the second transmembrane segment (TM2), we explored the action of this determinant by using protease protection analysis of mutant L proteins. We demonstrated that neither the disruption of a leucine zipper-like motif by multiple alanine substitutions nor the flanking charges of TM2 affected the topological reorientation of L. The dispensability of both putative subunit interaction modules argues against a link betwe…

A photoswitchable helical peptide with light-controllable interface/transmembrane topology in lipidic membranes

2021

Summary The spontaneous insertion of helical transmembrane (TM) polypeptides into lipid bilayers is driven by three sequential equilibria: solution-to-membrane interface (MI) partition, unstructured-to-helical folding, and MI-to-TM helix insertion. A bottleneck for understanding these three steps is the lack of experimental approaches to perturb membrane-bound hydrophobic polypeptides out of equilibrium rapidly and reversibly. Here, we report on a 24-residues-long hydrophobic α-helical polypeptide, covalently coupled to an azobenzene photoswitch (KCALP-azo), which displays a light-controllable TM/MI equilibrium in hydrated lipid bilayers. FTIR spectroscopy reveals that trans KCALP-azo folds…

Membrane topology of gp41 and amyloid precursor protein: Interfering transmembrane interactions as potential targets for HIV and Alzheimer treatment

2009

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…

Insertion and Topology of a Plant Viral Movement Protein in the Endoplasmic Reticulum Membrane

2002

Virus-encoded movement proteins (MPs) mediate cell-to-cell spread of viral RNA through plant membranous intercellular connections, the plasmodesmata. The molecular pathway by which MPs interact with viral genomes and target plasmodesmata channels is largely unknown. The 9-kDa MP from carnation mottle carmovirus (CarMV) contains two potential transmembrane domains. To explore the possibility that this protein is in fact an intrinsic membrane protein, we have investigated its insertion into the endoplasmic reticulum membrane. By using in vitro translation in the presence of dog pancreas microsomes, we demonstrate that CarMV p9 inserts into the endoplasmic reticulum without the aid of any addi…

Permeabilization of the erythrocyte membrane with streptolysin O allows access to the vacuolar membrane of Plasmodium falciparum and a molecular anal…

1997

The SARS-CoV-2 envelope (E) protein has evolved towards membrane topology robustness.

2021

- Single-spanning SARS-CoV-2 envelope (E) protein topology is a major determinant of protein quaternary structure and function. - Charged residues distribution in E protein sequences from highly pathogenic human coronaviruses (i.e., SARS-CoV, MERS-CoV and SARS-CoV-2) stabilize Ntout-Ctin membrane topology. - E protein sequence could have evolved to ensure a more robust membrane topology from MERS-CoV to SARS-CoV and SARS-CoV-2.

A photoswitchable helical peptide with light-controllable interface / transmembrane topology in lipidic membranes

2021

AbstractAccording to the three-step model, the spontaneous insertion and folding of helical transmembrane (TM) polypeptides into lipid bilayers is driven by three sequential equilibria: solution-to-membrane interface (MI) partition, unstructured-to-helical folding, and MI-to-TM helix insertion. However, understanding these three steps with molecular detail has been challenged by the lack of suitable experimental approaches to rapidly and reversibly perturb membrane-bound hydrophobic polypeptides out of equilibrium. Here, we report on a 24-residues-long hydrophobic α-helical polypeptide, covalently coupled to an azobenzene photoswitch (KCALP-azo), which displays a light-controllable TM/MI eq…

Development and characterization of a 293 cell line with regulatable expression of the hepatitis B virus large envelope protein

2004

During the life cycle of hepatitis B virus (HBV) the large L envelope protein plays a pivotal role that is related to its peculiar dual transmembrane topology. To study the complex structure and diverse functions of L under regulated conditions of production, a human 293 cell line stably expressing L under the control of the ecdysone-inducible promoter was generated. Cells demonstrated stringent dose- and time-dependent kinetics of induction with undetectable background expression in the absence of the inducer. Temporal control of L expression allowed to trace (i) its posttranslational reorientation resulting in the mixed topology; (ii) its spatial redistribution from the endoplasmic reticu…

The catalytic activity of the endoplasmic reticulum-resident protein microsomal epoxide hydrolase towards carcinogens is retained on inversion of its…

1996

Diol epoxides formed by the sequential action of cytochrome P-450 and the microsomal epoxide hydrolase (mEH) in the endoplasmic reticulum (ER) represent an important class of ultimate carcinogenic metabolites of polycyclic aromatic hydrocarbons. The role of the membrane orientation of cytochrome P-450 and mEH relative to each other in this catalytic cascade is not known. Cytochrome P-450 is known to have a type I topology. According to the algorithm of Hartman, Rapoport and Lodish [(1989) Proc. Natl. Acad. Sci. U.S.A. 86, 5786–5790], which allows the prediction of the membrane topology of proteins, mEH should adopt a type II membrane topology. Experimentally, mEH membrane topology has been …