65 research outputs found
Molecular Function of TCF7L2: Consequences of TCF7L2 Splicing for Molecular Function and Risk for Type 2 Diabetes.
No full textTCF7L2 harbors the variant with the strongest effect on type 2 diabetes (T2D) identified to date, yet the molecular mechanism as to how variation in the gene increases the risk for developing T2D remains elusive. The phenotypic changes associated with the risk genotype suggest that T2D arises as a consequence of reduced islet mass and/or impaired function, and it has become clear that TCF7L2 plays an important role for several vital functions in the pancreatic islet. TCF7L2 comprises 17 exons, five of which are alternative (ie, exons 4 and 13-16). In pancreatic islets four splice variants of TCF7L2 are predominantly expressed. The regulation of these variants and the functional consequences at the protein level are still poorly understood. A clear picture of the molecular mechanism will be necessary to understand how an intronic variation in TCF7L2 can influence islet function
Context dependence of protein secondary structure formation: the three-dimensional structure and stability of a hybrid between chymotrypsin inhibitor 2 and helix E from subtilisin Carlsberg
No full textThe loop region of chymotrypsin inhibitor 2 from barley has been employed as a scaffold for testing the intrinsic propensity of a peptide fragment to form a secondary structure. The helix formation of the nine amino acid residue segment Lys-Gln- Ala-Val- Asp- Asn- Ala-Tyr-Ala of helix E from subtilisin Carlsberg has been studied by the construction of a hybrid consisting of chymotrypsin inhibitor 2 (CI2) where part of the active loop has been replaced by the nonapeptide. An expression system for a truncated form of C12 where the 19 structureless residues of the N-terminus have been removed and Leu20 replaced by methionyl was constructed from the entire 83-residue wild-type C12 gene by polymerase chain reaction methodology. The gene encoding the hybrid was constructed from the truncated inhibitor gene. The stability of the truncated inhibitor and of the hybrid toward guanidinium chloride denaturation was examined. From these measurements, the energy of unfolding in pure water was extrapolated to 30.5 1.0 kJ/mol for the truncated inhibitor and 10.9 f 0.3 kJ/mol for the hybrid. These energies show that the stability of C12 is unaffected by the N-terminal truncation but severely decreased by the loop mutations. The three-dimensional structure of the hybrid protein has been determined in solution by nuclear magnetic resonance spectroscopy using 893 distance restraints and 84 torsional angle restraints. The average rootmean-square deviation (rmsd) of 15 structures compared to their geometrical average was 0.8 f 0.2 A for heavy backbone atoms and 1.3 * 0.2 A for all heavy atoms. The inserted peptide segment does not form an a-helix in the new structural context whereas the structure of the C12 scaffold turns out to be amazingly conserved
alpha(1)-Microglobulin: a yellow-brown lipocalin
No full textalpha(1)-Microglobulin, also called protein HC, is a lipocalin with immunosuppressive properties. The protein has been found in a number of vertebrate species including frogs and fish. This review summarizes the present knowledge of its structure, biosynthesis, tissue distribution and immunoregulatory properties. alpha(1)-Microglobulin has a yellow-brown color and is size and charge heterogeneous. This is caused by an array of small chromophore prosthetic groups, attached to amino acid residues at the entrance of the lipocalin pocket. A gene in the lipocalin cluster encodes alpha(1)-microglobulin together with a Kunitz-type proteinase inhibitor, bikunin. The gene is translated into the alpha(1)-microglobulin-bikunin precursor, which is subsequently cleaved and the two proteins secreted to the blood separately. alpha(1)-Microglobulin is found in blood and in connective tissue in most organs. It is most abundant at interfaces between the cells of the body and the environment, such as in lungs, intestine, kidneys and placenta. alpha(1)-Microglobulin inhibits immunological functions of white blood cells in vitro, and its distribution is consistent with an anti-inflammatory and protective role in vivo
Vesicular structures formed from barley wort proteins and iso-humulone
No full textIn beer, the main amphiphilic components are protein and iso-humulone. Two major populations of protein are identified as lipid transfer protein (LTP) (9.7 kDa) and protein Z (43 kDa). In this paper, protein and iso-humulone are extracted from barley malt and hop, respectively, based on the brewing process. Mixtures of protein and iso-humulone are mixed at different concentrations and centrifuged. Supernatants are analyzed by asymmetric flow field-flow fractionation (AF4) coupled to UV with multi-angle light scattering (MALS) detection as well as by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE). The presence of aggregates and their structures are investigated by light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that protein and iso-humulone can form aggregates from molecular level by AF4-UV-MALS and SDS-PAGE. The interaction is shown as solution depletion which is analyzed by AF4-UV-MALS. With 300 mg/L iso-humulone and 3 g/L protein in bulk, the decrease of protein peak levels off. The peak of protein Z is preferentially decreased as an effect of iso-humulone being present, suggesting that interaction between these populations is favored. The iso-humulone/protein aggregates consist of both undefined irregular aggregates as well as spherical aggregates. The spherical aggregates are observed in light microscopy, SEM and TEM. From SEM, it is clear that there are two types of spherical aggregates: rough and smooth. With TEM it can be observed that the smooth aggregates consist of a thin layer of the aggregated proteins and iso-humulone enclosing a liquid domain. This structure can best be described as an iso-humulone/protein vesicle. The rough vesicles are formed by further precipitation at the surface of the smooth vesicles
Vesicular structures formed from barley wort proteins and iso-humulone
No full textIn beer, the main amphiphilic components are protein and iso-humulone. Two major populations of protein are identified as lipid transfer protein (LTP) (9.7 kDa) and protein Z (43 kDa). In this paper, protein and iso-humulone are extracted from barley malt and hop, respectively, based on the brewing process. Mixtures of protein and iso-humulone are mixed at different concentrations and centrifuged. Supernatants are analyzed by asymmetric flow field-flow fractionation (AF4) coupled to UV with multi-angle light scattering (MALS) detection as well as by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE). The presence of aggregates and their structures are investigated by light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that protein and iso-humulone can form aggregates from molecular level by AF4-UV-MALS and SDS-PAGE. The interaction is shown as solution depletion which is analyzed by AF4-UV-MALS. With 300 mg/L iso-humulone and 3 g/L protein in bulk, the decrease of protein peak levels off. The peak of protein Z is preferentially decreased as an effect of iso-humulone being present, suggesting that interaction between these populations is favored. The iso-humulone/protein aggregates consist of both undefined irregular aggregates as well as spherical aggregates. The spherical aggregates are observed in light microscopy, SEM and TEM. From SEM, it is clear that there are two types of spherical aggregates: rough and smooth. With TEM it can be observed that the smooth aggregates consist of a thin layer of the aggregated proteins and iso-humulone enclosing a liquid domain. This structure can best be described as an iso-humulone/protein vesicle. The rough vesicles are formed by further precipitation at the surface of the smooth vesicles
Competitive adsorption of proteins from total hen egg yolk during emulsification
No full textIn this article, the competitive adsorption of egg yolk proteins at oil/water interfaces during emulsification is studied. By using two-dimensional polyacrylamide electrophoresis and mass spectrometry, it was possible to characterize and identify adsorbing and non-adsorbing protein species. The egg yolk contains proteins with a wide range of molecular weights and pI. Lipoproteins adsorbed selectively throughout the pH range investigated. It is suggested that selectivity is determined by the average hydrophobic and hydrophilic domain lengths in the protein sequences where long average hydrophobic domain lengths result in high affinity for the interface and thus strong preferential adsorption
Competitive adsorption of proteins from total hen egg yolk during emulsification
No full textIn this article, the competitive adsorption of egg yolk proteins at oil/water interfaces during emulsification is studied. By using two-dimensional polyacrylamide electrophoresis and mass spectrometry, it was possible to characterize and identify adsorbing and non-adsorbing protein species. The egg yolk contains proteins with a wide range of molecular weights and pI. Lipoproteins adsorbed selectively throughout the pH range investigated. It is suggested that selectivity is determined by the average hydrophobic and hydrophilic domain lengths in the protein sequences where long average hydrophobic domain lengths result in high affinity for the interface and thus strong preferential adsorption
Competitive adsorption of water soluble plasma proteins from egg yolk at the oil/water interface
No full textWater soluble plasma proteins were fractionated from hen's egg yolk, and the molecular weight and pI of the most abundant protein species were characterized with gel electrophoresis. The proteins were identified by mass spectrometry. The protein fraction was used to produce oil-in-water emulsions, both at various protein concentrations and at various pH values, and the surface load was determined through serum depletion. The competitive adsorption was studied through the determination of nonadsorbing species with gel electrophoresis. The results show that it was possible to form an oil-in-water emulsion for which droplet size and maximum surface load depended on the protein concentration and pH. Serum albumin and YGP40 adsorbed selectively at the oil/water interface throughout the pH range investigated, and for albumin the selectivity increased close to its pI. It is suggested that this selective adsorption is due to long hydrophobic stretches in the polypeptide chain, which are present in the selectively adsorbing species but absent in less adsorbing species
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