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11.
Membrane phosphatidylcholine homeostasis is maintained in part by a sensing device in the key regulatory enzyme, CTP:phosphocholine cytidylyltransferase (CCT). CCT responds to decreases in membrane phosphatidylcholine content by reversible membrane binding and activation. Two prominent isoforms, CCTα and -β2, have nearly identical catalytic domains and very similar membrane binding amphipathic helical (M) domains but have divergent and structurally disordered N-terminal (N) and C-terminal phosphorylation (P) regions. We found that the binding affinity of purified CCTβ2 for anionic membranes was weaker than CCTα by more than an order of magnitude. Using chimeric CCTs, insertion/deletion mutants, and truncated CCTs, we show that the stronger affinity of CCTα can be attributed in large part to the electrostatic membrane binding function of the polybasic nuclear localization signal (NLS) motif, present in the unstructured N-terminal segment of CCTα but lacking in CCTβ2. The membrane partitioning of CCTβ2 in cells enriched with the lipid activator, oleic acid, was also weaker than that of CCTα and was elevated by incorporation of the NLS motif. Thus, the polybasic NLS can function as a secondary membrane binding motif not only in vitro but in the context of cell membranes. A comparison of phosphorylated, dephosphorylated, and region P-truncated forms showed that the in vitro membrane affinity of CCTβ2 is more sensitive than CCTα to phosphorylation status, which antagonizes membrane binding of both isoforms. These data provide a model wherein the primary membrane binding motif, an amphipathic helical domain, works in collaboration with other intrinsically disordered segments that modulate membrane binding strength. The NLS reinforces, whereas the phosphorylated tail antagonizes the attraction of domain M for anionic membranes. 相似文献
12.
Laczkó-Dobos H Todinova SJ Sözer Ö Komenda J Kis M Sallai A Dobrikova AG Ughy B Debreczeny M Gombos Z Apostolova EL Domonkos I 《Photosynthesis research》2011,107(3):237-246
We used differential scanning calorimetry (DSC) as a technique capable of identifying photosynthetic complexes on the basis of their calorimetric transitions. Annotation of thermal transitions was carried out with thylakoid membranes isolated from various photosynthetic mutants of Synechocystis sp. PCC6803. The thylakoid membranes exhibited seven major DSC bands between 40 and 85°C. The heat sorption curves were analyzed both by mathematical deconvolution of the overall endotherms and by a subsequent annealing procedure. The successive annealing procedure proved to be more reliable technique than mathematical deconvolution in assigning thermal transitions. The main DSC band, around 47°C, resulting from the high enthalpy change that corresponds to non-interacting complex of PSII, was assigned using the PSI-less/apcE(-) mutant cells. Another band around 68-70°C relates to the denaturation of PSII surrounded by other proteins of the photosynthetic complexes in wild type and PSI-less/apcE(-) cells. A further major transition found at 82-84°C corresponds to the PSI core complex of wild type and PSII-deficient BE cells. Other transition bands between 50-67 and 65-75°C are believed to relate to ATP synthase and cytochrome b(6)f, respectively. These thermal transitions were obtained with thylakoids isolated from PSI(-)/PSII(-) mutant cells. Some minor bands determined at 59 and 83-84°C correspond to an unknown complex and NADH dehydrogenase, respectively. These annotations were done by PSI-less/apcE(-) and PSI(-)/PSII(-) mutants. 相似文献
13.
De Klerk Geert-Jan Brugge Jolanda Ter Marinova Svetla 《Plant Cell, Tissue and Organ Culture》1997,50(1):39-44
The production of an antifungal spirostanol saponin designated SC-1 has been detected in cell suspension cultures of the Mexican
species Solanum chrysotrichum. Batch cultures of a cell suspension obtained from hypocotyl derived calluses of this species
were grown for 25 days in shake flasks containing Murashige & Skoog (MS) medium. Throughout the growth cycle, fresh and dry
weight, SC-1 yield, and uptake of sucrose, glucose and fructose were determined. The effects of inoculum size and sucrose
concentration on the biomass accumulation and synthesis of the active metabolite, were studied. The maximum SC-1 production,
above 14 mg.g−1 (which was fifty times that of field grown plants), was reached after 20 days using a 2% inoculum and complete MS medium
supplemented with 2 mgl−1 2,4-D, 2 mg l−1kinetin, and sucrose between 30 and 45 gl−1.
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This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
Lidiya Angelova Michèle Dalgalarrondo Ignat Minkov Svetla Danova Nicolai Kirilov Julia Serkedjieva Jean-Marc Chobert Thomas Haertlé Iskra Ivanova 《Biochimica et Biophysica Acta (BBA)/General Subjects》2006
The aim of this study was to purify and characterise a novel protease inhibitor (PISC-2002) isolated from culture supernatants of Streptomyces chromofuscus. PISC-2002 was purified by anion-exchange chromatography, and RP-HPLC analysis. PISC-2002 had a molecular mass of 11.2 kDa and a high content of hydrophobic amino acids and proline. N-terminal sequence gave two sequences differing by one residue. The main sequence is ASLPAVSALVLTV and the shorter sequence is SLPAVSALVLTV. This shows its homology to Streptomyces subtilisin inhibitor family. Besides its large spectrum of powerful inhibitory activities against various serine proteases, PISC-2002 displayed significant antiviral effect against influenza virus A/Rostock/34 (H7N7). 相似文献
15.
Angelova L Dalgalarrondo M Minkov I Danova S Kirilov N Serkedjieva J Chobert JM Haertlé T Ivanova I 《Biochimica et biophysica acta》2006,1760(8):1210-1216
The aim of this study was to purify and characterise a novel protease inhibitor (PISC-2002) isolated from culture supernatants of Streptomyces chromofuscus. PISC-2002 was purified by anion-exchange chromatography, and RP-HPLC analysis. PISC-2002 had a molecular mass of 11.2 kDa and a high content of hydrophobic amino acids and proline. N-terminal sequence gave two sequences differing by one residue. The main sequence is ASLPAVSALVLTV and the shorter sequence is SLPAVSALVLTV. This shows its homology to Streptomyces subtilisin inhibitor family. Besides its large spectrum of powerful inhibitory activities against various serine proteases, PISC-2002 displayed significant antiviral effect against influenza virus A/Rostock/34 (H7N7). 相似文献
16.
Structural and functional analysis of glycosylated Cu/Zn-superoxide dismutase from the fungal strain Humicola lutea 103 总被引:2,自引:0,他引:2
Dolashka-Angelova P Stevanovic S Dolashki A Angelova M Serkedjieva J Krumova E Pashova S Zacharieva S Voelter W 《Biochemical and biophysical research communications》2004,317(4):1006-1016
The fungal strain Humicola lutea 103 produces a naturally glycosylated Cu/Zn-superoxide dismutase (Cu/ZnSOD) (HLSOD). To improve its yield, the effect of increased concentration of Cu2+ (from 1 to 750 microg/ml) on growth and enzyme biosynthesis was studied. The primary structure of this fungal enzyme has been determined by Edman degradation of peptide fragments derived from proteolytic digest. A single chain of the protein, consisting of 152 amino acid residues, reveals a very high degree (74-85%) of structural homology in comparison to the amino acid sequences of other fungal Cu/ZnSODs. The difference of the molecular masses of H. lutea Cu/ZnSOD, measured by MALDI-MS (15,935 Da) and calculated by its amino acid sequence (15,716 Da), is attributed to the carbohydrate chain of one mole of N-acetylglucosamine, attached to the N-glycosylation site Asn23-Glu-Ser. HLSOD protected mice from mortality after experimental influenza A/Aichi/2/68 (H3N2) virus infection. Using the glycosylated HLSOD, the survival rate is increased by 66% (protective index=86.1%) and the survival time prolonged by 5.2 days, similar to the application of ribavarin, while non-glycosylated bovine SOD conferred lower protection. 相似文献
17.
Vassileva S Tzvetkova B 《Zeitschrift für Naturforschung. C, Journal of biosciences》2003,58(5-6):381-385
The studied problem is of commercial interest because whey, the cultivation substrate, is a waste by-product from the transformation of milk into cheese and casein. Investigations on the influence of the dilution rate (D) on the bioproductivity of lactose-utilizing yeasts were carried out with two model strains--the oxidative strain Candida blankii 35 and the fermentative strain Candida pseudotropicalis 11. The increase of D led to the different changes in productivity. The best synthesizing ability of both continuously cultivated strains is established at D = 0.4 [h-1] despite the different type of metabolism. The oxidative strain C. blankii 35 is more effective in comparison with the fermentative strain C. pseudotropicalis 11 because of its ability to synthesize 1.5 fold higher biomass and protein yields. These experimental facts were proved also by simulative research with a Fuzzy Knowledge-Based System (FKBS) developed for modeling the influence of D on several process variables. 相似文献
18.
Yang X Tomov V Kurteva S Wang L Ren X Gorny MK Zolla-Pazner S Sodroski J 《Journal of virology》2004,78(23):12975-12986
The core of the gp120 glycoprotein from human immunodeficiency virus type 1 (HIV-1) is comprised of three major structural domains: the outer domain, the inner domain, and the bridging sheet. The outer domain is exposed on the HIV-1 envelope glycoprotein trimer and contains binding surfaces for neutralizing antibodies such as 2G12, immunoglobulin G1b12, and anti-V3 antibodies. We expressed the outer domain of HIV-1(YU2) gp120 as an independent protein, termed OD1. OD1 efficiently bound 2G12 and a large number of anti-V3 antibodies, indicating its structural integrity. Immunochemical studies with OD1 indicated that antibody responses against the outer domain of the HIV-1 gp120 envelope glycoprotein are rare in HIV-1-infected human sera that potently neutralize the virus. Surprisingly, such outer-domain-directed antibody responses are commonly elicited by immunization with recombinant monomeric gp120. Immunization with soluble, stabilized HIV-1 envelope glycoprotein trimers elicited antibody responses that more closely resembled those in the sera of HIV-1-infected individuals. These results underscore the qualitatively different humoral immune responses elicited during natural infection and after gp120 vaccination and help to explain the failure of gp120 as an effective vaccine. 相似文献
19.
Diapause-destined embryos of the crustacean, Artemia franciscana, accumulate large amounts of an oligomeric, heat-stable, molecular chaperone termed artemin, a cysteine-enriched ferritin
homologue. In this study, cysteines 22, 61, 166, and 172 of artemin were substituted with alanines, respectively yielding
ArtC22A, ArtC61A, ArtC166A, and ArtC172A. Wild-type and modified artemins were synthesized in transformed bacteria and purified.
As measured by heat-induced denaturation of citrate synthase in vitro, each substitution reduced chaperone activity, with
ArtC172A the least active. Protein modeling indicated that C172 is close to a region of surface hydrophobicity, also present
in ferritin, suggesting that this site contributes to chaperone activity. Only slight differences in oligomer molecular mass
were apparent between artemin variants, but ArtC22A and ArtC61A displayed significantly reduced thermostability, perhaps due
to the disruption of an inter-subunit disulphide bridge. In contrast, ArtC172A was thermostable, reflecting the location of
C172 on the oligomer surface and that it contributes minimally to artemin stabilization. To our knowledge, this is the initial
study of structure/function relationships within a ferritin homologue of importance in diapause and the first to indicate
that a defined region of hydrophobicity contributes to artemin and ferritin chaperoning. 相似文献
20.
Suhrcke M Stuckler D Suk JE Desai M Senek M McKee M Tsolova S Basu S Abubakar I Hunter P Rechel B Semenza JC 《PloS one》2011,6(6):e20724
There is concern among public health professionals that the current economic downturn, initiated by the financial crisis that started in 2007, could precipitate the transmission of infectious diseases while also limiting capacity for control. Although studies have reviewed the potential effects of economic downturns on overall health, to our knowledge such an analysis has yet to be done focusing on infectious diseases. We performed a systematic literature review of studies examining changes in infectious disease burden subsequent to periods of crisis. The review identified 230 studies of which 37 met our inclusion criteria. Of these, 30 found evidence of worse infectious disease outcomes during recession, often resulting from higher rates of infectious contact under poorer living circumstances, worsened access to therapy, or poorer retention in treatment. The remaining studies found either reductions in infectious disease or no significant effect. Using the paradigm of the "SIR" (susceptible-infected-recovered) model of infectious disease transmission, we examined the implications of these findings for infectious disease transmission and control. Key susceptible groups include infants and the elderly. We identified certain high-risk groups, including migrants, homeless persons, and prison populations, as particularly vulnerable conduits of epidemics during situations of economic duress. We also observed that the long-term impacts of crises on infectious disease are not inevitable: considerable evidence suggests that the magnitude of effect depends critically on budgetary responses by governments. Like other emergencies and natural disasters, preparedness for financial crises should include consideration of consequences for communicable disease control. 相似文献