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Hydrophobic Regions (hydrophobic + regions)
Selected AbstractsSelenium affects biosilica formation in the demosponge Suberites domunculaFEBS JOURNAL, Issue 15 2005Effect on gene expression, spicule formation Selenium is a trace element found in freshwater and the marine environment. We show that it plays a major role in spicule formation in the demosponge Suberites domuncula. If added to primmorphs, an in vitro sponge cell culture system, it stimulates the formation of siliceous spicules. Using differential display of transcripts, we demonstrate that, after a 72-h exposure of primmorphs to selenium, two genes are up-regulated; one codes for selenoprotein M and the other for a novel spicule-associated protein. The deduced protein sequence of selenoprotein M (14 kDa) shows characteristic features of metazoan selenoproteins. The spicule-associated protein (26 kDa) comprises six characteristic repeats of 20 amino acids, composed of 10 distinct hydrophobic regions (, 9 amino acids in length). Recombinant proteins were prepared, and antibodies were raised against these two proteins. Both were found to stain the central axial filament, which comprises the silicatein, as well as the surface of the spicules. In the presence of selenium, only the genes for selenoprotein M and spicule-associated protein are up-regulated, whereas the expression of the silicatein gene remains unchanged. Finally we show that, in the presence of selenium, larger silica aggregates are formed. We conclude that selenium has a stimulatory effect on the formation of siliceous spicules in sponges, and it may be involved in the enzymatic synthesis of biosilica components. [source] R120G ,B-crystallin promotes the unfolding of reduced ,-lactalbumin and is inherently unstableFEBS JOURNAL, Issue 3 2005Teresa M. Treweek ,-Crystallin is the principal lens protein which, in addition to its structural role, also acts as a molecular chaperone, to prevent aggregation and precipitation of other lens proteins. One of its two subunits, ,B-crystallin, is also expressed in many nonlenticular tissues, and a natural missense mutation, R120G, has been associated with cataract and desmin-related myopathy, a disorder of skeletal muscles [Vicart P, Caron A, Guicheney P, Li Z, Prevost MC, Faure A, Chateau D, Chapon F, Tome F, Dupret JM, Paulin D & Fardeau M (1998) Nat Genet20, 92,95]. In the present study, real-time 1H-NMR spectroscopy showed that the ability of R120G ,B-crystallin to stabilize the partially folded, molten globule state of ,-lactalbumin was significantly reduced in comparison with wild-type ,B-crystallin. The mutant showed enhanced interaction with, and promoted unfolding of, reduced ,-lactalbumin, but showed limited chaperone activity for other target proteins. Using NMR spectroscopy, gel electrophoresis, and MS, we observed that, unlike the wild-type protein, R120G ,B-crystallin is intrinsically unstable in solution, with unfolding of the protein over time leading to aggregation and progressive truncation from the C-terminus. Light scattering, MS, and size-exclusion chromatography data indicated that R120G ,B-crystallin exists as a larger oligomer than wild-type ,B-crystallin, and its size increases with time. It is likely that removal of the positive charge from R120 of ,B-crystallin causes partial unfolding, increased exposure of hydrophobic regions, and enhances its susceptibility to proteolysis, thus reducing its solubility and promoting its aggregation and complexation with other proteins. These characteristics may explain the involvement of R120G ,B-crystallin with human disease states. [source] Identification of regions of leukotriene C4 synthase which direct the enzyme to its nuclear envelope localizationJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2006Jesper Svartz Abstract Leukotrienes (LTs) are fatty acid derivatives formed by oxygenation of arachidonic acid via the 5-lipoxygenase (5-LO) pathway. Upon activation of inflammatory cells 5-LO is translocated to the nuclear envelope (NE) where it converts arachidonic acid to the unstable epoxide LTA4. LTA4 is further converted to LTC4 by conjugation with glutathione, a reaction catalyzed by the integral membrane protein LTC4 synthase (LTC4S), which is localized on the NE and endoplasmic reticulum (ER). We now report the mapping of regions of LTC4S that are important for its subcellular localization. Multiple constructs encoding fusion proteins of green fluorescent protein (GFP) as the N-terminal part and various truncated variants of human LTC4S as C-terminal part were prepared and transfected into HEK 293/T or COS-7 cells. Constructs encoding hydrophobic region 1 of LTC4S (amino acids 6,27) did not give distinct membrane localized fluorescence. In contrast hydrophobic region 2 (amino acids 60,89) gave a localization pattern similar to that of full length LTC4S. Hydrophobic region 3 (amino acids 114,135) directed GFP to a localization indistinguishable from that of full length LTC4S. A minimal directing sequence, amino acids 117,132, was identified by further truncation. The involvement of the hydrophobic regions in the homo-oligomerization of LTC4S was investigated using bioluminescence resonance energy transfer (BRET) analysis in living cells. BRET data showed that hydrophobic regions 1 and 3 each allowed oligomerization to occur. These regions most likely form transmembrane helices, suggesting that homo-oligomerization of LTC4S is due to helix,helix interactions in the membrane. J. Cell. Biochem. 98: 1517,1527, 2006. © 2006 Wiley-Liss, Inc. [source] Synthesis and characterization of sulfonated-fluorinated, hydrophilic-hydrophobic multiblock copolymers for proton exchange membranesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2009Xiang Yu Abstract Hydrophilic/hydrophobic block copolymers as proton exchange membranes (PEMs) has become an emerging area of research in recent years. These copolymers were obtained through moderate temperature (, 100 °C) coupling reactions, which minimize the ether-ether interchanges between hydrophobic and hydrophilic telechelic oligomers via a nucleophilic aromatic substitution mechanism. The hydrophilic blocks were based on the nucleophilic step polymerization of 3,3,-disulfonated, 4,4,-dichlorodiphenyl sulfone with an excess 4,4,-biphenol to afford phenoxide endgroups. The hydrophobic (fluorinated) blocks were largely based on decafluoro biphenyl (excess) and various bisphenols. The copolymers were obtained in high molecular weights and were solvent cast into tough membranes, which had nanophase separated hydrophilic and hydrophobic regions. The performance and structure-property relationships of these materials were studied and compared to random copolymer systems. NMR results supported that the multiblock sequence had been achieved. They displayed superior proton conductivity, due to the ionic proton conducting channels formed through the self-assembly of the sulfonated blocks. The nano-phase separated morphologies of the copolymer membranes were studied and confirmed by atomic force microscopy. Through control of a variety of parameters, including ion exchange capacity and sequence lengths, performances as high, or even higher than those of the state-of-the-art PEM, Nafion, were achieved. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1038,1051, 2009 [source] In vivo analysis of the lumenal binding protein (BiP) reveals multiple functions of its ATPase domainTHE PLANT JOURNAL, Issue 6 2007Christopher James Snowden Summary The endoplasmic reticulum (ER) chaperone binding protein (BiP) binds exposed hydrophobic regions of misfolded proteins. Cycles of ATP hydrolysis and nucleotide exchange on the ATPase domain were shown to regulate the function of the ligand-binding domain in vitro. Here we show that ATPase mutants of BiP with defective ATP-hydrolysis (T46G) or ATP-binding (G235D) caused permanent association with a model ligand, but also interfered with the production of secretory, but not cytosolic, proteins in vivo. Furthermore, the negative effect of BiP(T46G) on secretory protein synthesis was rescued by increased levels of wild-type BiP, whereas the G235D mutation was dominant. Unexpectedly, expression of a mutant BiP with impaired ligand binding also interfered with secretory protein production. Although mutant BiP lacking its ATPase domain had no detrimental effect on ER function, expression of an isolated ATPase domain interfered with secretory protein synthesis. Interestingly, the inhibitory effect of the isolated ATPase was alleviated by the T46G mutation and aggravated by the G235D mutation. We propose that in addition to its role in ligand release, the ATPase domain can interact with other components of the protein translocation and folding machinery to influence secretory protein synthesis. [source] Hexaquacobalt(II) bis(5-hydroxy-7-methoxy-4-oxo-2-phenyl-4H -chromene-6-sulfonate) tetrahydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2008Wu-Wu Li The title compound, [Co(H2O)6](C16H11O7S)2·4H2O, with cobalt(II) at the centre of symmetry, exhibits alternating hydrophilic and hydrophobic regions. Hydrophilic regions are generated by O,H...O hydrogen bonds among sulfonate groups, involving solvent water molecules and coordinated water molecules; ,,, stacking interactions assemble the flavone skeletons into columns which form the hydrophobic regions. A three-dimensional network is built up from an extensive array of hydrogen bonds, ,,, stacking interactions and electrostatic interactions between the cation and anion. As a salt of the sulfonated derivative of naturally occurring tectochrysin (5-hydroxy-7-methoxyflavone), this compound offers enhanced solubility and potential biological activity over the natural product. [source] Ion channel formation and membrane-linked pathologies of misfolded hydrophobic proteins: The role of dangerous unchaperoned moleculesCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 9 2002Joseph I Kourie Summary 1.,Protein,membrane interaction includes the interaction of proteins with intrinsic receptors and ion transport pathways and with membrane lipids. Several hypothetical interaction models have been reported for peptide-induced membrane destabilization, including hydrophobic clustering, electrostatic interaction, electrostatic followed by hydrophobic interaction, wedge × type incorporation and hydrophobic mismatch. 2.,The present review focuses on the hypothesis of protein interaction with lipid membranes of those unchaperoned positively charged and misfolded proteins that have hydrophobic regions. We advance the hypothesis that protein misfolding that leads to the exposure of hydrophobic regions of proteins renders them potentially cytotoxic. Such proteins include prion, amyloid , protein (A,P), amylin, calcitonin, serum amyloid and C-type natriuretic peptides. These proteins have the ability to interact with lipid membranes, thereby inducing membrane damage and cell malfunction. 3.,We propose that the most significant mechanism of membrane damage induced by hydrophobic misfolded proteins is mediated via the formation of ion channels. The hydrophobicity based toxicity of several proteins linked to neurodegenerative pathologies is similar to those observed for antibacterial toxins and viral proteins. 4.,It is hypothesized that the membrane damage induced by amyloids, antibacterial toxins and viral proteins represents a common mechanism for cell malfunction, which underlies the associated pathologies and cytotoxicity of such proteins. [source] | |||||||||||||