Membrane Proteins (Total 807762 Papers Found)

Sorting of ubiquitinated endosomal membrane proteins into the MVB pathway is executed by the class E Vps protein complexes ESCRT-I, -II, and -III, and the AAA-type ATPase Vps4. This study characterizes ESCRT-II, a soluble approximately 155 kDa protein complex formed by the class E Vps proteins Vps22, Vps25, and Vps36. This protein complex transiently associates with the endosomal membrane and thereby initiates the formation of ESCRT-III, a membrane-associated protein complex that functions immed ...
Occludin is an integral membrane protein of the epithelial cell tight junction (TJ). Its potential role in coordinating structural and functional events of TJ formation has been suggested recently. Using a rat salivary gland epithelial cell line (Pa-4) as a model system, we have demonstrated that occludin not only is a critical component of functional TJs but also controls the phenotypic changes associated with epithelium oncogenesis. Transfection of an oncogenic Raf-1 into Pa-4 cells resulted i ...
An engineered precursor protein that sticks in the import site of isolated yeast mitochondria can be specifically photo-crosslinked to a mitochondrial outer-membrane protein of relative molecular mass 42,000 (42K). This protein (termed import-site protein 42 or ISP 42) is exposed on the mitochondrial surface; antibodies against it block protein import into mitochondria. ISP 42 is the first identified component of the putative transmembrane machinery that imports proteins into mitochondria. ...
GAP-43, a neuron specific growth-associated protein, is selectively distributed to the axonal domain in developing neurons; it is absent from dendrites and their growth cones. Using immunofluorescence microscopy, we have further examined the distribution of GAP-43 during the development of hippocampal neurons in culture, in order to determine when this polarized distribution arises. Cultured hippocampal neurons initially extend several short processes which have the potential to become either ax ...
Photoaffinity labeling of a soybean cotyledon membrane fraction identified a sucrose-binding protein (SBP). Subsequent studies have shown that the SBP is a unique plasma membrane protein that mediates the linear uptake of sucrose in the presence of up to 30 mM external sucrose when ectopically expressed in yeast. Analysis of the SBP-deduced amino acid sequence indicates it lacks sequence similarity with other known transport proteins. Data presented here, however, indicate that the SBP shares si ...
A type-specific antigen (TSA) in Rickettsia tsutsugamushi is a 56-kDa protein located on the rickettsial surface. The gene (tsg56) encoding the TSA was isolated from R. tsutsugamushi Gilliam strain. Sequencing revealed an open reading frame of 1572 bp encoding a 524-amino acid (aa) protein with an Mr of 56,053. The deduced aa sequence consists of a 22-aa signal sequence and the mature TSA sequence (502 aa; Mr 53,803), whose N-terminal portion has the aa sequence determined directly in our previo ...
Subcellular compartmentalization, cell growth, hormone secretion and neurotransmission require rapid, targeted, and regulated membrane fusion. Fusion entails extensive lipid rearrangements by two apposed (docked) membrane vesicles, joining their membrane proteins and lipids and mixing their luminal contents without lysis. Fusion of membranes in the secretory pathway involves Rab GTPases; their bound 'effector' proteins, which mediate downstream steps; SNARE proteins, which can 'snare' each other ...
Directed cell migration and axonal guidance are essential steps in neural development. Both processes are controlled by specific guidance cues that activate the signaling cascades that ultimately control cytoskeletal dynamics. Another essential step in migration and axonal guidance is the regulation of plasmalemma turnover and exocytosis in leading edges and growth cones. However, the cross talk mechanisms linking guidance receptors and membrane exocytosis are not understood. Netrin-1 is a chemo ...
The 4 kDa beta-amyloid peptide that forms the amyloid fibrils in the brain parenchyma of Alzheimer's disease patients is derived from the larger integral membrane protein, the amyloid precursor protein. In the nonamyloidogenic pathway, alpha-secretase cleaves the amyloid precursor protein within the beta-amyloid domain, releasing an extracellular portion and thereby preventing deposition of the intact amyloidogenic peptide. The release of the amyloid precursor protein from both SH-SY5Y and IMR-3 ...
A novel transmembrane protein (designated X7365) containing two follistatin modules and an epidermal growth factor (EGF) domain has been described in the hypothalamic-pituitary axis of Xenopus laevis. We have now cloned the highly conserved mouse orthologue (M7365), and its mRNA was detected in many mesodermal and (neuro)ectodermal tissues in 8.5-day-old mouse embryos. During further development, M7365 mRNA expression became restricted to certain regions in the brain and to ganglia. In the adult ...
Plasmodium falciparum is an intracellular parasite of the red blood cell. During development it exports proteins which are transported to specific locations within the host erythrocyte. We have begun to identify and characterize exported membrane proteins of P. falciparum in order to obtain specific marker molecules for the study of the mechanisms involved in the distribution of parasite-derived proteins within the host cell. In this report we describe the characterization of a 35 kDa protein wh ...
Although Bordetella pertussis, the etiologic agent of whooping cough, adheres and grows on the ciliated epithelium of the respiratory tract, it has been extensively studied only in liquid cultures. In this work, the phenotypic expression of B. pertussis in biofilm growth is described as a first approximation of events that may occur in the colonization of the host. The biofilm developed on polypropylene beads was monitored by chemical methods and Fourier transform infrared (FT-IR) spectroscopy. ...
The active site of liver-specific, drug-metabolizing cytochrome P450 (CYP) monooxygenases is deeply buried in the protein and is connected to the protein surface through multiple tunnels, many of which were found open in different CYP crystal structures. It has been shown that different tunnels could serve as ligand passage routes in different CYPs. However, it is not understood whether one CYP uses multiple routes for substrate access and product release and whether these routes depend on ligan ...
Red cell membrane protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and direct quantitation by radioimmunoassay or cytofluorometry defines four distinct subsets of patients with hereditary spherocytosis: Patients with isolated spectrin deficiency, combined spectrin and ankyrin deficiency, band 3 deficiency, and protein 4.2 deficiency. In regard to the first group, only one mutation of beta spectrin has been reported in the literature. We describe a spectrin ...
The Candida albicans CDR1 and CDR2 genes code for highly homologous ATP-binding cassette (ABC) transporters which are overexpressed in azole-resistant clinical isolates and which confer resistance to multiple drugs by actively transporting their substrates out of the cells. These transporters are formed by two homologous halves, each with an intracellular domain containing an ATP-binding site followed by a membrane-associated domain. We have expressed Cdr1p and Cdr2p in Saccharomyces cerevisiae ...
Indole derivative 1 interferes with the interaction of the HIV surface protein gp120 with the host cell receptor CD4. The 4-fluoro derivative 2 exhibited markedly enhanced potency and was bioavailable in the rat, dog, and cynomolgus monkey when administered orally as a solution formulation. However, aqueous suspensions of 2 were poorly bioavailable, indicative of dissolution-limited absorption. The 7-azaindole derivative 3, BMS-378806, exhibited improved pharmaceutical properties while retaining ...
Intestinal dietary triacylglycerol absorption is a multi-step process. Triacylglycerol exit from the endoplasmic reticulum (ER) is the rate-limiting step in the progress of the lipid from its apical absorption to its basolateral membrane export. Triacylglycerol is transported from the ER to the cis Golgi in a specialized vesicle, the pre-chylomicron transport vesicle (PCTV). The vesicle-associated membrane protein 7 (VAMP7) was found to be more concentrated on PCTVs compared with ER membranes. V ...
Nematode-trapping fungi are soil-living fungi that capture and kill nematodes using special hyphal structures called traps. They display a large diversity of trapping mechanisms and differ in their host preferences. To provide insights into the genetic basis for this variation, we compared the transcriptome expressed by three species of nematode-trapping fungi (Arthrobotrys oligospora, Monacrosporium cionopagum and Arthrobotrys dactyloides, which use adhesive nets, adhesive branches or constrict ...
Recently, we showed that neutral sphingomyelinase (N-SMase) is concentrated at the endothelial cell surface in caveolae and is activated to produce ceramide in an acute and transient manner by increase in flow rate and pressure in rat lung vasculature (Czarny M, Liu J, Oh P, and Schnitzer JE, J Biol Chem 278: 4424-4430, 2003). Here, we report further on our investigations of this new acute mechanotransduction pathway. We employed three experimental models to explore the role of N-SMase and ceram ...
The role of SPARC in the in vivo lung response to crocidolite asbestos was addressed by instillation of crocidolite asbestos in a series of wild-type or SPARC-null mice. Animals were sacrificed at one week, one month, and three months post-instillation to assess the impact of SPARC on multiple stages in the development of fibrosis. RNA was harvested from 10 animals/time point, pooled, and used to probe a mouse array containing approximately 10,000 probes. Gene expression data were analyzed for f ...
Plasmodesmata, dynamic pore structures that traverse plant cell walls, function in cytoplasmic transport between contiguous cells. Cell walls containing embedded plasmodesmata were isolated from mesocotyls of etiolated maize seedlings. Proteins associated with the isolated walls were separated by SDS-PAGE and antibodies were generated against a 41 kDa protein, one of several associated with this wall fraction. Immunoblot analysis showed that the 41 kDa polypeptide was also associated with other ...
In the brain, glia represents the cell population that expresses the highest level of connexins, the membrane protein constituents of gap junction channels and hemichannels. This statement has initially led to propose the existence of a glial syncytium. Since then, functional studies have established that connexin channel-mediated communication between glial cells was more restricted and plastic that primarily thought. In particular, this is the case for astrocytes that form functional networks ...
Here we test whether the incorporation of docosahexaenoic acid (DHA, 22:6), an (n-3) fatty acid, into lymphocyte membranes affects the expression of the surface proteins Thy-1.2 and CD8. DHA was incorporated into splenocytes by three methods: feeding mice diets containing menhaden (fish) oil, fusing splenocytes with DHA-containing phosphatidylcholine vesicles, and culturing splenocytes with DHA. Thy-1.2 and CD8 expression were measured by flow cytometry and complement-mediated lysis using a pane ...
The whole genome information on pathogenic bacteria opened a new era of medical microbiology. Bacteria have a variety of strategies to survive in human body against host defense. Bacteria colonizing on the mucous cell surface and proliferate extracellularly have developed a number of paralogs of surface proteins for antigenic variation, while bacteria which proliferate intracellularly have acquired genes for invasion and anti-active oxygen. The obligate intracellular parasites, Rickettsiae and C ...
Efficient T cell activation depends on the engagement of both TCR and CD28, although the molecular mechanisms that control this signal integration are not fully understood. Using fluorescence resonance energy transfer , we show that T cell activation can drive a reorientation of the cytosolic tails of the CD28 dimer. However, this is not mediated through CD28 ligand binding. Rather, TCR signaling itself mediates this con-formation change in CD28. We also show that TCR signaling can induce CD28 ...
Atherosclerosis is the leading cause for cardiovascular mortality. We determined the effect of multi-antigenic construct expressing three peptides AHC (ApoB100, HSP60 and outer membrane protein of chlamydia pneumonia) in stabilizing advanced atherosclerosis in Apobtm2Sgy/Ldlrtm1Her/J mice. Atherosclerosis was induced by feeding high fat diet (HFD) to mice for 10 weeks, followed by five oral dosing with purified AHC or ovalbumin on alternate days and continued on HFD for another 10 weeks. Toleran ...
The naturally antibiotic-resistant bacterium Burkholderia pseudomallei is the causative agent of melioidosis, a disease with stubbornly high mortality and a complex, protracted treatment regimen. The worldwide incidence of melioidosis is likely grossly underreported, though it is known to be highly endemic in northern Australia and Southeast Asia. Bacterial disulfide bond proteins (DSB) catalyze the oxidative folding and isomerization of disulfide bonds in substrate proteins. In the present stud ...
Transmembrane proteins allow cells to extensively communicate with the external world in a very accurate and specific way. They form principal nodes in several signaling pathways and attract large interest in therapeutic intervention, as the majority pharmaceutical compounds target membrane proteins. Thus, according to the current genome annotation methods, a detailed structural/functional characterization at the protein level of each of the elements codified in the genome is also required. The ...
A method of separating envelope proteins by two-dimensional polyacrylamide gel electrophoresis is described. Escherichia coli envelopes (inner and outer membranes) were prepared by French pressing and washed by repeated centrifugation. Membrane proteins were solubilized with guanidine thiocyanate and were dialyzed against urea prior to two-dimensional electrophoretic analysis. The slab gel apparatus and conditions were similar to the technique developed by Metz and Bogorad (1974) for the separat ...
Non-linear electron spin resonance (EPR) techniques suitable for measuring proximity relationships in membranes are reviewed. These were developed during the past decade in order to measure changes sensitively in the spin-lattice relaxation time (T1) of nitroxyl spin labels covalently attached to membrane lipids or proteins. In combination with paramagnetic quenching agents and double spin-labelling, the methods were further developed for distance measurements. Selected examples are given to ill ...
Personalized medicine requires the development of a wide array of biomarker diagnostic assays, reflecting individual variations and thus allowing tailored therapeutic interventions. Membrane proteins comprise approximately 30% of total human proteins; they play a key role in various physiological functions and pathological conditions, although, currently, only a limited number of membrane proteins are applied as biomarkers. In many normal tissues, cell surface membrane proteins are not easily ac ...
Understanding how membrane proteins interact with detergents is of fundamental and practical significance in structural and chemical biology as well as in nanobiotechnology. Current methods for inspecting protein-detergent complex (PDC) interfaces require high concentrations of protein and are of low throughput. Here, we describe a scalable, spectroscopic approach that uses nanomolar protein concentrations in native solutions. This approach, which is based on steady-state fluorescence polarizati ...
Phospholamban (PLN) is a dynamic single-pass membrane protein that inhibits the flow of Ca(2+) ions into the sarcoplasmic reticulum (SR) of heart muscle by directly binding to and inhibiting the SR Ca(2+)ATPase (SERCA). The PLN monomer is the functionally active form that exists in equilibrium between ordered (T state) and disordered (R state) states. While the T state has been fully characterized using a hybrid solution/solid-state NMR approach, the R state structure has not been fully portraye ...
We used biotinylation and streptavidin affinity chromatography to label and enrich proteins from apical and basolateral membranes of rat kidney inner medullary collecting ducts (IMCDs) prior to LC-MS/MS protein identification. To enrich apical membrane proteins and bound peripheral membrane proteins, IMCDs were perfusion-labeled with primary amine-reactive biotinylation reagents at 2 degrees C using a double barreled pipette. The perfusion-biotinylated proteins and proteins bound to them were is ...
The membrane of the delta-aminolaevulinic acid synthase (EC. 2.3.1.37) deficient mutant of Bacillus subtilis growing in the presence of delta-aminolaevulinic acid differs only to a limited extent from the wild type. In haemin-containing medium, however, significant differences are observed as regards the osmotic stability of the protoplasts and the membrane protein composition. ...
High-throughput crystallization of biological macromolecules is usually performed on multi-well plates, the design of which needs to address different and sometimes conflicting requirements. In this regard, handling of membrane proteins presents a particular challenge owing to the common use of detergents with associated effects on surface tension. Reported here is the design of a new crystallization plate, termed the MPI tray, which is optimized for UV and visible imaging with membrane protein ...
Lysine methylation and methyltransferases are widespread in the third domain of life, archaea. Nevertheless, the effects of methylation on archaeal proteins wait to be defined. Here, we report that recombinant sisMCM, an archaeal homolog of Mcm2-7 eukaryotic replicative helicase, is methylated by aKMT4 in vitro. Mono-methylation of these lysine residues occurs coincidently in the endogenous sisMCM protein purified from the hyperthermophilic Sulfolobus islandicus cells as indicated by mass spectr ...
Introduction About 150 different proteins and glycoproteins have been characterized on the surface of various leucocyte populations that are not widely expressed on other cell types [l]. These proteins are candidates for mediation of the many functions that depend on interactions at the leucocyte surface. With regard to lymphocytes, the types of functions that can be expected involve receptors for soluble factors such as cytokines, those involved in antigen recognition on T-cells and B-cells and ...
The tranquilizer reserpine has several effects on adrenal medullary chromaffin-granule membrane vesicles (ghosts). At low concentrations (0.20 +/0 0.12 nmol/mg of membrane protein), reserpine inhibits proton-linked epinephrine uptake but does not affect transmembrane pH and electrical potential gradients. Reserpine apparently binds to and blocks the catecholamine translocator. At intermediate concentrations (14.3 +/- 4.8 nmol/mg of membrane protein), reserpine abolishes the ATP-dependent enhance ...
After endocytosis, a selective endocytic recycling process returns many endocytosed molecules back to the plasma membrane. The RAB-10/Rab10 GTPase is known to be a key recycling regulator for specific cargo molecules. New evidence, focused on C. elegans RAB-10 in polarized epithelia, points to a key role of RAB-10 in the regulation of endosomal phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) levels. In turn, PI(4,5)P2 levels strongly influence the recruitment of many peripheral membrane protei ...
Polymeric immunoglobulin receptor (secretory component, SC) is an intergral membrane protein synthesized by secretory epithelial cells and by hepatocytes of certain mammals. However, the synthesis, display and function of SC in human liver is not well characterized. We therefore sought evidence for SC synthesis by human liver using specific antibodies to SC to screen a library of phage expression vectors (λgtll) containing cDNA copies of human liver messenger RNA.In initial screening, 3×105 ph ...
Specific protein interactions in Escherichia coli outer membrane were analyzed using chemical cross-linking with truly cleavable reagents and symmetrical two-dimensional sodium dodecyl sulphate/polyacrylamide gel electrophoresis. The major outer membrane proteins were shown to form cross-linked complexes. These include multimers of lambda receptor, protein I, II, III and the free form of lipoprotein. Lipoprotein was also found to be cross-linked to proteins II and III. The identity of many of th ...
A system which incorporates amino acids into proteins of chloroplast membranes of Chlamydomonas reinhardti is described. It consists of chloroplast ribosomes bound to thylakoid membranes and cell extract. mRNA is present in this thylakoid-ribosome complex, since neither initiation nor RNA synthesis seems to be required for amino acid incorporation. Incorporation requires ATP, GTP and a soluble portion of cell extract. It is inhibited by chloramphenicol, but not cycloheximide. Most incorporated r ...
The research on protein-polymer conjugates by grafting from the surface of proteins has gained significant interest in the last decade. While there are many studies with globular proteins, membrane proteins have remained untouched to the best of our knowledge. In this study, we established the conjugate formation with a class of transmembrane proteins and grow polymer chains from the ferric hydroxamate uptake protein component A (FhuA; a β-barrel transmembrane protein of Escherichia coli). As t ...
A quantitative proteomic analysis of the membrane of the archaeon Sulfolobus solfataricus P2 using iTRAQ was successfully demonstrated in this technical note. The estimated number of membrane proteins of this organism is 883 (predicted based on Gravy score), corresponding to 30% of the total number of proteins. Using a modified iTRAQ protocol for membrane protein analysis, of the 284 proteins detected, 246 proteins were identified as membrane proteins, while using an original iTRAQ protocol, 147 ...