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51.
Vesicular transport of proteins and lipids between distinct subcellular compartments is directly responsible for generating and maintaining the structure of the organelles of the secretory and endocytic pathways in eukaryotic cells. Rapid advances in a variety of experimental systems have resulted in the identification of molecules involved in late steps of the transport process. This article presents a general paradigm for vesicular fusion and reviews the available experimental evidence. 相似文献
52.
François Baneyx Amanda Ayling Terry Palumbo Daniel Thomas George Georgiou 《Applied microbiology and biotechnology》1991,36(1):14-20
Summary The expression of many secreted recombinant proteins in Gram-negative bacteria is limited by degradation in the periplasmic space. We have previously shown that the production of protein A--lactamase, a secreted fusion protein highly sensitive to proteolysis in Escherichia coli, can be increased in mutant strains deficient in up to three cell-envelope-associated proteolytic activities. In this work we investigated the effect of fermentation conditions on suppressing any residual proteolytic activity in various protease-deficient strains. Optimal production of the fusion protein was observed in cells grown under mildly acidic conditions (5.5pH6.0) and at low temperatures. These conditios were shown to specifically decrease the rate of proteolysis. In addition, a further increase in production was observed in cultures supplemented with 0.5 to 0.75 mM zinc chloride. This may relate to the inhibition of a cell envelope protease by Zn2+ ions.
Offsprint requests to: G. Georgiou 相似文献
53.
Françoise Seigle-Murandi Serge Krivobok Régine Steiman Georges-André Thiault Jean-Louis Benoit-Guyod 《Applied microbiology and biotechnology》1991,34(4):436-440
Summary The biotransformation of 2-acetylthiophene by 800 strains of micromycetes has been investigated. Among them, 460 strains have been selected on solid media and cultivated in a liquid synthetic medium. Of these, 106 strains were able to completely deplete 2-acetylthiophene with or without production of intermediary metabolites. 2-Thienylglyoxylic acid was not detected but 72 strains produced 2-thiophenecarboxylic acid. Among them, eight strains have been selected for further optimization of this bioconversion. 相似文献
54.
Cyclin B in Xenopus oocytes: implications for the mechanism of pre-MPF activation. 总被引:25,自引:9,他引:16
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Using a polyclonal antibody raised against B2 cyclin from Xenopus laevis, we show that prophase-arrested Xenopus oocytes contain a stockpile of cyclin B2 protein. During progesterone-induced maturation, an increase in the synthesis of cyclin B2 is observed, although Western blotting experiments show that this new synthesis does not significantly increase the mass of cyclin over the maternal stockpile. In the oocyte cyclin B2 is already present in two forms which differ in the extent of phosphorylation, but the phosphorylated form becomes predominant as oocytes progress towards germinal vesicle breakdown (GVBD), coincident with cdc2 protein kinase activation. These two events do not depend upon formation of a new complex between cyclin and cdc2 protein kinase, since these two proteins are already found associated in resting oocytes, prior to activation of the kinase. 相似文献
55.
René Roy François D. Tropper Anna Romanowska Marie Letellier Luc Cousineau Serge J. Meunier Janusz Boratyński 《Glycoconjugate journal》1991,8(2):75-81
Starting from peracetylated chloro- or bromo-glycosyl donors ofN-acetylneurmainic acid,N-acetylglucosamine, glucose and lactose, the correspondingp-formylphenyl glycosides were synthesized stereospecifically under phase transfer catalysed conditions at room temperature in yields of 38–67%. After Zemplén de-O-acetylation, the formyl groups were directly and chemoselectively coupled to the lysine residues of bovine serum albumin by reductive amination using sodium cyanoborohydride. The conjugation reactions were followed as a function of time and under a series of different molar ratios of the reactants to provide glycoconjugates of varying degree of antigenicities. Thus, carbohydrate protein conjugates were made readily available using essentially two key reactions.Presented in part at the 15th International Carbohydrate Symposium, Yokohama, Japan, August 12–17, 1990. 相似文献
56.
Claude Sauvage Jean-François Rumigny Michel Maitre 《Molecular and cellular biochemistry》1991,107(1):65-77
Summary Three G proteins from human brain membranes were purified to near homogeneity by conventional techniques including preparative
electrophoresis. These G proteins were characterized by their ability to bind GTP, GDP and GTP analogs. Two of these proteins
have molecular weights of 50,000 (G50) and 36,000 (G36), as determined on SDS-gels. G36 was ADP-ribosylated by pertussis toxin. Thus, G50 could represent a Gsα subunit, whereas G36 could be Giα or Goα. G50 was phosphorylated by cAMP dependent protein kinase and protein kinase C. G36 was phosphorylated by a protein kinase independent of calcium and phospholipid, a proteolytic product of protein kinase C,
analogous to protein kinase M. Phosphorylation of G36 by this protein kinase induced a dramatic decrease in its GTPase activity. The third G protein, of molecular weight 22,000
probably belongs to the group of monomeric G proteins possessing functional similarities withras gene products. The regulation of G proteins involving calcium-dependent and independent pathways is delineated. 相似文献
57.
Monique Berthelon Catherine Caillaud Françoise Rey Philippe Labrune Dominique Melle Josué Feingold Jean Frézal Marie-Louise Briard Jean-Pierre Farriaux Pierre Guibaud Hubert Journel Bernard Le Marec Nicole Maurin Jean-Louis Nivelon Henri Plauchu Jean-Marie Saudubray Philippe Tron Jean Rey Arnold Münnich Stanislas Lyonnet 《Human genetics》1991,86(4):355-358
Summary A total of 252 chromosomes from 126 patients with phenylalanine hydroxylase (PAH) deficiencies were analyzed for both mutant genotypes and restriction fragment length polymorphism (RFLP) haplotypes at the PAH locus. The mutant genes studied originated either from Western Europe (116 alleles) or from Mediterranean countries (136 alleles). Only 27% of all mutant alleles were found to carry identified mutations, particularly mutations at codon 252 (2.3%), 261 (7.5%), 280 (6.3%), 408 (3.5%) and at the splice donor site of intron 12 (6.3%). The mutant genotypes were associated with RFLP haplotypes 7, 1, 38, 2 and 3 at the PAH locus respectively. Except for the splice mutation of intron 12, these associations were preferential, but not exclusive, since the other four mutations were found on the background of at least two RFLP haplotypes. These results, together with the observation that 85% of PAH deficient patients are heterozygotes for their mutant genotypes, emphasize the great heterogeneity of PAH deficiencies in Mediterranean countries and hamper systematic DNA testing for carrier status in this population. 相似文献
58.
Clinical and molecular heterogeneity of phenylalanine hydroxylase deficiencies in France 总被引:20,自引:10,他引:10
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Franoise Rey Monique Berthelon Catherine Caillaud Stanislas Lyonnet Vronique Abadie Flicienne Blandin-Savoja Josu Feingold Jean-Marie Saudubray Jean Frzal Arnold Munnich Jean Rey 《American journal of human genetics》1988,43(6):914-921
RFLPs of 68 normal and 74 mutant alleles at the phenylalanine hydroxylase (PAH) locus were determined in 37 French kindreds. A total of 23 haplotypes, including 18 normal and 16 mutant alleles, were observed. Two-thirds of all mutant alleles were confined within only four haplotypes, while the last third was accounted for by 12 haplotypes, including eight haplotypes absent from Caucasian pedigrees reported thus far. Several mutant haplotypes were present in typical phenylketonuria only, others were present in variants only, and some were present in both. In addition, a particular mutant haplotype (haplotype 2) was found to harbor different mutations in our series, resulting in either typical phenylketonuria or in mild hyperphenylalaninemias. The diploid combination of so many mutant haplotypes in PAH-deficient patients and of compound heterozygosity at the PAH locus in southern Europe might account for the broad spectrum of individual phenotypes observed in France. 相似文献
59.
C Gautier D Bazile J Paoletti 《Biochemical and biophysical research communications》1988,154(1):252-257
We have investigated by means of absorbance measurements at 310 nm the binding of alpha-anomeric or beta-anomeric tetrathymidylates covalently substituted at their 3' end by an intercalating agent (oxazolopyridocarbazolium), to poly(rA). Taking into account the strong autoaggregation of the free ligands, we have derived the binding parameters corresponding to the [alpha] and the [beta] ligands. The affinity of the alpha-anomer for poly(rA) is higher than the affinity of the beta-anomer in accordance with the Tm studies conducted on such a system. 相似文献
60.
Two Down syndrome patients with rec(21),dupq,inv(21)(p11;q2109) from a familial pericentric inversion 总被引:2,自引:0,他引:2
Aneusomie de recombinaison arose from a familial pericentric inversion of a chromosome 21. Two female patients had a typical Down syndrome; one of them had slight psychomotor retardation. There was partial trisomy 21q2109----qter in these two patients but ZnCu SOD activity was normal. 相似文献