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Comparative Structural (comparative + structural)
Selected AbstractsComparative Structural, Emulsifying, and Biological Properties of 2 Major Canola Proteins, Cruciferin and NapinJOURNAL OF FOOD SCIENCE, Issue 3 2008J. Wu ABSTRACT:, Canola is an economically important farm-gate crop in Canada. To further explore the potential of canola protein as value-added food and nutraceutical ingredients, a better understanding of fundamental properties of 2 major canola proteins is necessary. Two major protein components, cruciferin and napin, were isolated from defatted canola meal by Sephacryl S-300 gel filtration chromatography. SDS-PAGE showed that cruciferin consists of more than 10 polypeptides, and noncovalent links are more important than disulphide bonds in stabilizing the structural conformation. Napin consists of 2 polypeptides and is stabilized primarily by disulphide bonds. Purified cruciferin showed 1 major endothermic peak at 91 °C compared with that of 110 °C for napin. Emulsion prepared by cruciferin showed significant higher specific surface area and lower particle size than that of napin. The study indicated that the presence of napin could detrimentally affect the emulsion stability of canola protein isolates. Hydrolysates from cruciferin and napin showed potent angiotensin I-converting enzyme inhibitory activity (IC50: 0.035 and 0.029 mg/mL, respectively), but weaker than that of canola protein isolate hydrolysate (IC50: 0.015 mg/mL). [source] The SmtB/ArsR family of metalloregulatory transcriptional repressors: structural insights into prokaryotic metal resistanceFEMS MICROBIOLOGY REVIEWS, Issue 2-3 2003Laura S. Busenlehner Abstract The SmtB/ArsR family of prokaryotic metalloregulatory transcriptional repressors represses the expression of operons linked to stress-inducing concentrations of di- and multivalent heavy metal ions. Derepression results from direct binding of metal ions by these homodimeric ,metal sensor' proteins. An evolutionary analysis, coupled with comparative structural and spectroscopic studies of six SmtB/ArsR family members, suggests a unifying ,theme and variations' model, in which individual members have evolved distinct metal selectivity profiles by alteration of one or both of two structurally distinct metal coordination sites. These two metal sites are designated ,3N (or ,3) and ,5 (or ,5C), named for the location of the metal binding ligands within the known or predicted secondary structure of individual family members. The ,3N/,3 sensors, represented by Staphylococcus aureus pI258 CadC, Listeria monocytogenes CadC and Escherichia coli ArsR, form cysteine thiolate-rich coordination complexes (S3 or S4) with thiophilic heavy metal pollutants including Cd(II), Pb(II), Bi(III) and As(III) via inter-subunit coordination by ligands derived from the ,3 helix and the N-terminal ,arm' (CadCs) or from the ,3 helix only (ArsRs). The ,5/,5C sensors Synechococcus SmtB, Synechocystis ZiaR, S. aureus CzrA, and Mycobacterium tuberculosis NmtR form metal complexes with biologically required metal ions Zn(II), Co(II) and Ni(II) characterized by four or more coordination bonds to a mixture of histidine and carboxylate ligands derived from the C-terminal ,5 helices on opposite subunits. Direct binding of metal ions to either the ,3N or ,5 sites leads to strong, negative allosteric regulation of repressor operator/promoter binding affinity, consistent with a simple model for derepression. We hypothesize that distinct allosteric pathways for metal sensing have co-evolved with metal specificities of distinct ,3N and ,5 coordination complexes. [source] Characterization and functional analysis of ABSCISIC ACID INSENSITIVE3 -like genes from Physcomitrella patensTHE PLANT JOURNAL, Issue 6 2006Heather H. Marella Summary Although the moss Physcomitrella patens is known to respond to abscisic acid (ABA) by activating gene expression, the transcriptional components involved have not been characterized. Initially, we used the ABA-responsive Em promoter from wheat linked to , -glucuronidase (GUS) to determine whether ABI3/VP1, transcriptional regulators in the ABA-signaling pathway in angiosperms, were similarly active in the ABA response of P. patens. We show by particle bombardment that ABI3 and VP1 affect Em,GUS expression in P. patens in a manner similar to angiosperms. We also show the involvement of ABI1 in the pathway, utilizing the abi1-1 mutant allele. We isolated three ABI3 -like genes from P. patens. Using an Em-like ABA-responsive promoter from P. patens (PpLea1), we demonstrate that PpABI3A, only in the presence of ABA, strongly enhances PpLea1,GUS expression in P. patens. PpABI3A also enhances ABA-induced Em,GUS expression in P. patens. In barley aleurone, PpABI3A transactivates Em,GUS but to a lesser extent than VP1 and ABI3. PpABI3A:GFP is localized to the nucleus of both protonemal cells and barley aleurone, indicating that the nuclear localization signals are conserved. We show that at least a part of the inability of PpABI3A to fully complement the phenotypes of the Arabidopsis abi3-6 mutant is due to a weak interaction between PpABI3A and the bZIP transcription factor ABI5, as assayed functionally in barley aleurone and physically in the yeast-two-hybrid assay. Our data clearly demonstrate that P. patens will be useful for comparative structural and functional studies of components in the ABA-response pathway such as ABI3. [source] Synthesis, and structural and morphological characterization of iron oxide,ion-exchange resin and ,cellulose nanocomposites,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 5 2001Lorenza Suber Abstract The synthesis and the comparative structural and morphological study of iron oxide nanoparticles in polystyrene-based ion-exchange resins and cellulosics are reported. The synthesis of magnetite was performed under nitrogen atmosphere by an in situ method in the presence of the matrix itself. Scanning and transmission electron microscopy measurements led to a detailed characterization of matrix morphology and of magnetic particle structure, size and morphology. The results show that the matrix influences the iron oxide particle size; the average size is about 7,nm in the resins and 25,nm in the celluloses. In the resins, particles are present inside the pores and as aggregates on the surface of the resin beads, whereas in the cellulose they are present on the surface and in the swollen network of the microfibers constituting the single fibers. Copyright © 2001 John Wiley & Sons, Ltd. [source] | |||||||||||||