Search results for "Membrane Biology"
showing 10 items of 12 documents
Organization into Higher Ordered Ring Structures Counteracts Membrane Binding of IM30, a Protein Associated with Inner Membranes in Chloroplasts and …
2016
The IM30 (inner membrane-associated protein of 30 kDa), also known as the Vipp1 (vesicle-inducing protein in plastids 1), has a crucial role in thylakoid membrane biogenesis and maintenance. Recent results suggest that the protein binds peripherally to membranes containing negatively charged lipids. However, although IM30 monomers interact and assemble into large oligomeric ring complexes with different numbers of monomers, it is still an open question whether ring formation is crucial for membrane interaction. Here we show that binding of IM30 rings to negatively charged phosphatidylglycerol membrane surfaces results in a higher ordered membrane state, both in the head group and in the inn…
The C-terminal Domains of Apoptotic BH3-only Proteins Mediate Their Insertion into Distinct Biological Membranes
2016
Changes in the equilibrium of pro- and anti-apoptotic members of the B-cell lymphoma-2 (Bcl-2) protein family in the mitochondrial outer membrane (MOM) induce structural changes that commit cells to apoptosis. Bcl-2 homology-3 (BH3)-only proteins participate in this process by either activating pro-apoptotic effectors or inhibiting anti-apoptotic components and by promoting MOM permeabilization. The association of BH3-only proteins with MOMs is necessary for the activation and amplification of death signals; however, the nature of this association remains controversial, as these proteins lack a canonical transmembrane sequence. Here we used an in vitro expression system to study the inserti…
Alix regulates egress of hepatitis B virus naked capsid particles in an ESCRT-independent manner
2010
Hepatitis B virus (HBV) is an enveloped DNA virus that exploits the endosomal sorting complexes required for transport (ESCRT) pathway for budding. In addition to infectious particles, HBV-replicating cells release non-enveloped (nucleo)capsids, but their functional implication and pathways of release are unclear. Here, we focused on the molecular mechanisms and found that the sole expression of the HBV core protein is sufficient for capsid release. Unexpectedly, released capsids are devoid of a detectable membrane bilayer, implicating a non-vesicular exocytosis process. Unlike virions, naked capsid budding does not require the ESCRT machinery. Rather, we identified Alix, a multifunctional …
Identification of Cysteine Residues in Human Cationic Amino Acid Transporter hCAT-2A That Are Targets for Inhibition by N-Ethylmaleimide
2013
In most cells, cationic amino acids such as l-arginine, l-lysine, and l-ornithine are transported by cationic (CAT) and y(+)L (y(+)LAT) amino acid transporters. In human erythrocytes, the cysteine-modifying agent N-ethylmaleimide (NEM) has been shown to inhibit system y(+) (most likely CAT-1), but not system y(+)L (Devés, R., Angelo, S., and Chávez, P. (1993) J. Physiol. 468, 753-766). We thus wondered if sensitivity to NEM distinguishes generally all CAT and y(+)LAT isoforms. Transport assays in Xenopus laevis oocytes established that indeed all human CATs (including the low affinity hCAT-2A), but neither y(+)LAT isoform, are inhibited by NEM. hCAT-2A inhibition was not due to reduced tran…
A chimera carrying the functional domain of the orphan protein SLC7A14 in the backbone of SLC7A2 mediates trans-stimulated arginine transport.
2012
In human skin fibroblasts, a lysosomal transport system specific for cationic amino acids has been described and named system c. We asked if SLC7A14 (solute carrier family 7 member A14), an orphan protein assigned to the SLC7 subfamily of cationic amino acid transporters (CATs) due to sequence homology, may represent system c. Fusion proteins between SLC7A14 and enhanced GFP localized to intracellular vesicles, co-staining with the lysosomal marker LysoTracker(®). To perform transport studies, we first tried to redirect SLC7A14 to the plasma membrane (by mutating putative lysosomal targeting motifs) but without success. We then created a chimera carrying the backbone of human (h) CAT-2 and …
Revisiting Plant Plasma Membrane Lipids in Tobacco: A Focus on Sphingolipids
2016
International audience; The lipid composition of plasma membrane (PM) and the corresponding detergent-insoluble membrane (DIM) fraction were analyzed with a specific focus on highly polar sphingolipids, so-called glycosyl inositol phosphorylceramides (GIPCs). Using tobacco (Nicotiana tabacum) 'Bright Yellow 2' cell suspension and leaves, evidence is provided that GIPCs represent up to 40 mol % of the PM lipids. Comparative analysis of DIMs with the PM showed an enrichment of 2-hydroxylated very-long-chain fatty acid-containing GIPCs and polyglycosylated GIPCs in the DIMs. Purified antibodies raised against these GIPCs were further used for immunogold-electron microscopy strategy, revealing …
A reduction of protein specific motions in co-ligated myoglobin embedded in a trehalose glass
2000
Protein Kinase C-dependent Ubiquitination and Clathrin-mediated Endocytosis of the Cationic Amino Acid Transporter CAT-1*
2011
Cationic amino acid transporter 1 (CAT-1) is responsible for the bulk of the uptake of cationic amino acids in most mammalian cells. Activation of protein kinase C (PKC) leads to down-regulation of the cell surface CAT-1. To examine the mechanisms of PKC-induced down-regulation of CAT-1, a functional mutant of CAT-1 (CAT-1-HA-GFP) was generated in which a hemagglutinin antigen (HA) epitope tag was introduced into the second extracellular loop and GFP was attached to the carboxyl terminus. CAT-1-HA-GFP was stably expressed in porcine aorthic endothelial and human epithelial kidney (HEK) 293 cells. Using the HA antibody internalization assay we have demonstrated that PKC-dependent endocytosis…
Structure-function analysis of peroxisomal ATP-binding cassette transporters using chimeric dimers
2014
Background: Peroxisomal ABC transporters are predicted to function as homodimers in mammals. [br/] Results: ABCD1 interacts with ABCD2. Chimeric proteins mimicking full-length dimers represent novel tools for functional study. Artificial homodimers and heterodimers are functional. [br/] Conclusion: Interchangeability between ABCD1 and ABCD2 is confirmed, but PUFA transport depends on ABCD2. [br/] Significance: For the first time, heterodimers in mammals are proven to be functional.[br/] ABCD1 and ABCD2 are two closely related ATP-binding cassette half-transporters predicted to homodimerize and form peroxisomal importers for fatty acyl-CoAs. Available evidence has shown that ABCD1 and ABCD2 …
How to Bridge the Gap Between Membrane Biology and Polymer Science
1986
Can polymer chemists contribute to the understanding or even mimicking of cell membrane functions and cell-cell interactions? Fascinated by the specificity and efficiency of, for example, the destruction of tumor cells by lymphocytes (1) and having in mind what biochemical analyses tell us about membrane composition, we may try to “synthesize” membrane and cell models. The commonly used model systems, such as planar lipid monolayers at the gas-water interface, bimolecular lipid membranes and spherical liposomes, are much less stable than natural membrane systems (Figure 1).