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Filtration and Membrane World: Protein Separations Soy protein concentrates are prepared by removing soluble sugars from defatted soy flakes or flours. Another modified, "second-generation" soy protein concentrate of improved functionality is produced by successive pressure and cavitation, such as centrifugal homogenation at elevated temperatures and slightly alkaline pH, a high-NSI soy protein concentrate can be obtained from one that originally had a low NSI value. It includes aqueous extraction of soluble proteins and carbohydrates from defatted soybean flakes or soy flour; separation of the insoluble residue, followed by precipitation of protein at mildly acidic conditions; separation and removal of the soluble carbohydrates, proteins, and salts; and washing and drying of the protein. www.membraneworld.com /psepars.html   (930 words)

Membrane protein - Wikipedia, the free encyclopedia A membrane protein is a protein molecule that is attached to, or associated with the membrane of a cell or an organelle. Membrane proteins can be classified into two groups, based on the strength of their association with the membrane. Integral and peripheral proteins may be post-translationally modified, with added fatty acid or prenyl chains, or GPI (glycosylphosphatidylinositol), which may be anchored in the lipid bilayer. en.wikipedia.org /wiki/Membrane_protein   (575 words)

cellmembrane Membranes are composed of phospholipids, proteins and carbohydrates arranged in a fluid mosaic structure, as shown in this diagram. Proteins comprise about 50% of the mass of membranes, and are responsible for most of the membrane's properties. Proteins on the inside surface of cell membranes are often attached to the cytoskeleton and are involved in maintaining the cell's shape, or in cell motility. www.biologymad.com /cells/cellmembrane.htm   (1771 words)

Globular and Membrane Protein Self-Assembly   (Site not responding. Last check: 2007-11-04) Most often this is accomplished by the aggregation of hydrophobic residues in the center of the protein, thus forcing hydrophilic residues to the surface of the protein. Membrane bound proteins are incorporated into the cellular membranes that surround cells and their compartments. In order for these proteins to perform their numerous functions (signal transduction, ion balance maintenance, molecular transport, electron transport, structure, etc.), they must be appropriately oriented and organized within the membrane. www.nanoword.net /library/weekly/blsaprotein2.php   (400 words)

Tim Stevens Home Site-Membrane Proteins:4. Membrane protein folding When proteins fold to their stable, native structures this entropic penalty is offset by the formation of bonds, both intramolecular and with solvent molecules. NMR experiments are limited to small molecular complexes (smaller than membrane proteins in detergent micelles) where the rate of tumbling of the particle under study is fast enough to average the chemical shift anisotropy and dipole-dipole interactions. If for example,a membrane protein forms an ion channel and there is a residue within the transmembrane domain which is essential to the function of the ion channel,then that residue may be placed within an environment where the helices are likely to form a pore (e.g. www.bio.cam.ac.uk /~tjs23/MembraneProteins_4Membraneproteinfolding.html   (4138 words)

Breakthrough: Structure of membrane protein described by Hebrew University, German researchers Membrane protein research is at the forefront of modern biological study, with great potential consequences for development of new medicinal treatments and genetic engineering of plants. The fatty cell membrane is impenetrable to most of these materials and signals; and it is therefore the proteins within the membranes that are responsible for the communication between the cell and its environment. Since the cell membrane proteins are exposed, in part, to areas extending outside the cells, the medicines are able to reach them without entering the cell itself. www.eurekalert.org /pub_releases/2005-08/thuo-bs080405.php   (631 words)

Determination of Membrane Protein Glycation in Diabetic Tissue After mixing thoroughly, the protein precipitate was obtained by centrifugation at 10,000 rpm for 10 minutes at 4°C. The protein pellet was washed twice with 1 mL water and redissolved in 1 mL of 0.1 M sodium phosphate buffer containing 1% sodium dodecyl sulfate (SDS) (pH 8.0). The glycation extent of total membrane protein from the intestine of diabetic rats was 4.89 nmol/mg protein (SD 0.48), whereas the corresponding value for normoglycemic rats was 2.23 nmol/mg protein (SD 0.64). Because membrane proteins play an important role in transporting nutrients and drugs in the intestine and various other organs in the body, the current protocol will be particularly useful to researchers investigating the role of membrane protein glycation in the pathology of aging and metabolic diseases such as diabetes. www.aapspharmsci.org /view.asp?art=ps010420   (3656 words)

InterPro: IPR003335 SecD/SecF/SecDF export membrane protein Proteins are produced in the cytoplasm as precursors, and require a chaperone subunit to direct them to the translocase component. The translocase protein subunits are encoded on the bacterial chromosome. The chaperone protein SecB [ 2 ] is a highly acidic homotetrameric protein that exists as a "dimer of dimers" in the bacterial cytoplasm. www.ebi.ac.uk /interpro/IEntry?ac=IPR003335   (3255 words)

[No title] Membrane flow through the cell is a highly dynamic process in which intracellular compartments communicate via tubulo-vesicular structures shuttling cargo molecules to their destinations. SNARE proteins are membrane-associated proteins that contain characteristic SNARE domains: heptad repeats 60 amino acids in length that are predicted to form coiled-coils. The PSI Centers are expected to solve large numbers of protein structures in a high-throughput fashion, but membrane proteins are not currently amenable to high throughput efforts. www.lycos.com /info/membrane--membrane-protein.html   (668 words)

Membrane Protein Pilot Project Membrane proteins are responsible for communication between the outside world and the chemical and biological factories housed inside the cell membranes. The membrane proteins are particularly difficult to structurally characterize. Fewer than two dozen membrane protein structures from the entire world of biology have been characterized to atomic resolution and many of these are at such modest resolution that functional mechanisms are not clear. magnet.fsu.edu /~mprotein/MBPweb/TBgrant.html   (324 words)

MEMBRANES Carbohydrates of membranes are present attached to protein or lipid as glycoprotein or glycolipid. The beta-subunit is a glycoprotein, with the carbohydrate on the external surface of the membrane. The receptor-insulin complex migrates to a region of the plasma membrane with the protein clathrin coating its inner surface. www-medlib.med.utah.edu /NetBiochem/membrane.htm   (2845 words)

MEMBRANE PROTEINE DATABASE Subunit stoichiometry of staphylococcal a-hemolysin in crystal and on membranes: a heptameric transmembrane pore. Structure of the protein subunits in the photosynthetic reaction centre of Rhodopseudomonas viridis at 3 Å resolution. Protein, lipid and water organization in bacteriorhodopsin crystals: a molecular view of the purple membrane at 1.9 Å resolution. sb20.lbl.gov /cobessi/membrane_struc.htm   (1992 words)

Rationalization of membrane protein crystallization with polyethylene glycol using a simple depletion model Biophysical ... An iron-containing protein that is important in cell respiration, cytochrome bc^sub 1^ complex (BC1), is used for the study. Compared to soluble proteins, the crystallization of membrane proteins is extremely difficult and a relatively small number of them have been crystallized so far despite their important biological roles. Membrane proteins are combined with detergents in solutions, and they form protein-detergent complexes (PDCs) (Garavito and Ferguson-Miller, 2001). www.findarticles.com /p/articles/mi_qa3938/is_200305/ai_n9273776   (927 words)

membrane protein folding The reserach of this group is focussed on the assembly of biomembranes in general and on the insertion and folding of transmembrane proteins into membranes in particular. Integral membrane proteins are usually very hydrophobic and insoluble in water. -barrel membrane proteins was mainly focussed on outer membrane protein A of E.coli. www.biologie.uni-konstanz.de /folding/home.html   (464 words)

Membrane Transport Mechanisms   (Site not responding. Last check: 2007-11-04) The center of the barrel could constitute a hole in the plasma membrane that is isolated from the lipid bilayer by an array of transmembrane domains around it. In practice, given the structure of known membrane proteins, these holes are only large enough to allow the passage of small molecules through the plasma membrane, almost always simple ions like hydrogen, potassium or sodium. Primary active transport involves using energy (usually through ATP hydrolysis) at the membrane protein itself to cause a conformational change that results in the transport of the molecule through the protein. web.mit.edu /esgbio/www/cb/membranes/transport.html   (738 words)

New routes to membrane protein structures Membrane proteins are essential for cellular life: they contribute to the multitude of processes whereby cells interact with their environment, generate energy and maintain their cellular milieu and structure. Due to the nature of their environment in the hydrophobic lipid bilayer, membrane proteins are generally much more difficult to study than are soluble proteins, a problem which becomes apparent both when trying to obtain crystals and when attempting to determine high-resolution structures of these proteins. In one interesting new methodology which was described, ternary micelles containing histidine-tagged membrane proteins, reconstitution lipids and detergent, are bound to a Ni functionalized lipid layer formed at an air−water interface (Figure 1). www.nature.com /embor/journal/v2/n3/full/embor460.html   (3524 words)

Mem-PER Eukaryotic Membrane Protein Traditional methods for isolation of membrane protein are tedious, timeconsuming, and require gradient separation and expensive ultracentrifugation equipment. Hydrophilic and hydrophobic (membrane protein) fractions were analyzed by Western blot with HRP-labeled secondary antibody followed by SuperSignal West Femto Chemiluminescent Substrate for four proteins from the cellular locations noted. Hydrophobic (membrane protein) fractions and corresponding hydrophilic fractions prepared with Mem-PER Reagents were analyzed by Western blot for VDAC (31 kDa), Flotillin-1 (48 kDa) and Cellugyrin (29 kDa). www.piercenet.com /Products/Browse.cfm?fldID=06010422   (468 words)

E-MeP: the European Membrane Protein Consortium This is being achieved by integrating the activities of many of the world leaders in membrane protein structural biology. Specifically, the heterologous production, purification and crystallisation of a library of bioinformatically-selected membrane proteins are being streamlined by elucidating the parameters responsible for success and failure at each of these key stages. In the process new technologies will be developed and commercialised to overcome existing bottlenecks peculiar to membrane protein structural genomics, which cannot be solved by existing methods. www.e-mep.org   (237 words)

Simultaneous assignment and structure determination of a membrane protein from NMR orientational restraints -- Marassi ... Almeida, F.C. and Opella, S.J. fd coat protein structure in membrane environments: Structural dynamics of the loop between the hydrophobic trans-membrane helix and the amphipathic in-plane helix. Bogusky, M.J., Leo, G.C., and Opella, S.J. Comparison of the dynamics of the membrane bound form of fd coat protein in micelles and in bilayers. Marassi, F.M. and Opella, S.J. A solid-state NMR index of membrane protein helical structure and topology. www.proteinscience.org /cgi/content/full/12/3/403   (4755 words)

Membrane Protein Folding We are pushing the envelope of what is currently possible for the structure determination of membrane proteins by NMR spectroscopy. To this end, we are working to increase expression levels of membrane proteins and we are developing protocols to refold membrane proteins in lipid and detergent environments. Secondary and tertiary structure formation of the beta-barrel membrane protein OmpA is synchronized and depends on membrane thickness. faculty.virginia.edu /tamm/pages/project_folding.html   (466 words)

InterPro: IPR003423 Outer membrane efflux protein The trimeric channel is composed of a 12 stranded all beta sheet barrel that spans the outer membrane, and a long all helical barrel that spans the periplasm. Examples include the Escherichia coli TolC outer membrane protein, which is required for proper expression of outer membrane protein genes; the Rhizobium nodulation protein; and the Pseudomonas FusA protein, which is involved in resistance to fusaric acid. Johnson J.M. Church G.M. Alignment and structure prediction of divergent protein families: periplasmic and outer membrane proteins of bacterial efflux pumps. www.ebi.ac.uk /interpro/IEntry?ac=IPR003423   (2917 words)

Explicit Membrane Protein Simulations in NAMD/VMD   Align the protein with the centre of the membrane. The membrane and protein are in the same position but we need to combine them so that the lipid and water molecules that are overlapping with the protein are deleted. NB – Proteins, even in crystals, are highly solvated – that is they contain a lot of water within the boundaries of the structure. mccammon.ucsd.edu /~rlaw/ctbp_workshop_rlaw.htm   (1906 words)

Membrane protein sequence analys This could also be seen in the dot plot analysis and in a sequence alignment of the first part of the protein with the last part. The structure of this protein is known (PDB 1JSQ). However, it is an outer-membrane protein that has a b-barrel structure that cannot be predicted by the current methods for transmembrane segment predictions. www.biol.lu.se /mibiol/research/wachen/membrane_proteins_answers2.htm   (508 words)

Arabidopsis Membrane Protein Library The Arabidopsis membrane protein library is a collection of polytopic membrane protein sequences (containing two or more predicted membrane spanning domains) from the model plant Arabidopsis thaliana. The protein sequences have been clustered into families based on sequence homology and the families have been assigned to functional categories where possible. Links are now available (on the left side menu) to other plant membrane protein sites. www.cbs.umn.edu /arabidopsis   (387 words)

Integral membrane protein - Wikipedia, the free encyclopedia Integral monotopic proteins are permanently attached to the membrane from one side. Membrane PDB Database of 3D structures of integral membrane proteins and hydrophobic peptides with emphasis on crystallization conditions Membrane proteins of known 3D structure from Stephen White laboratory en.wikipedia.org /wiki/Integral_membrane_protein   (376 words)

RFA-RM-07-003: Membrane Protein Production and Structure Determination (R01) This RFA solicits applications to enhance the rate of membrane protein structure determination and to facilitate the determination of membrane protein structures. http://www.mpibp-frankfurt.mpg.de/michel/public/memprotstruct.html)  This progress clearly demonstrates that obtaining membrane protein structures is feasible.  However, during this same decade the rate of soluble protein structure determination has accelerated greatly, and there remains a gap between the understanding of membrane proteins and their soluble protein counterparts (1). Innovations in both solid state and solution NMR spectroscopy methods to improve their applicability to larger size membrane proteins.  Improvements are needed in isotopic labeling methods and for data collection on limited samples with significant non-protein background signals from detergent and lipids. grants.nih.gov /grants/guide/rfa-files/RFA-RM-07-003.html   (5316 words)

Membrane Lecture Notes Trans-membrane proteins have membrane spanning portions containing alpha helically arranged sequences of 20-25 hydrophobic amino acids. At high temperatures cholesterol tends to reduce membrane fluidity, probably by interacting with the hydrocarbon tails of the phospholipid and glycolipid molecules. The binding of a membrane protein/glycoprotein to some other cellular or extracellular substance, molecule, ion, etc. can/will result in a 3-dimensional conformational change in that membrane protein. www.d.umn.edu /~sdowning/Membranes/lecturenotes.html   (530 words)

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