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101.
Quality control within the endoplasmic reticulum (ER) is thought to be mediated by the interaction of a folding protein with one or several resident ER proteins [1]. Protein disulphide isomerase (PDI) is one such ER resident protein that has been previously shown to interact with proteins during their folding and assembly pathways [2, 3]. It has been assumed that, as a consequence of this interaction, unassembled proteins are retained within the ER. Here, we experimentally show that this is indeed the case. We have taken advantage of our previous finding that PDI interacts with procollagen chains early on in their assembly pathway [2] to address the role of this protein in directly retaining unassembled chains within the ER. Our experimental approach involved expressing individual C-propeptide domains from different procollagen chains in mammalian cells and determining the ability of these domains to interact with PDI and to be secreted. The C-propeptide from the proalpha2(I) chain was retained within the cell, where it formed a complex with PDI. Conversely, the C-propeptide from the proalpha1(III) chain did not form a complex with PDI and was secreted. Both domains were secreted, however, from a stable cell line expressing a secreted form of PDI lacking its ER retrieval signal. Hence, we have demonstrated directly that the intracellular retention of one substrate for ER quality control is due to an interaction with PDI. 相似文献
102.
All the IgA1 proteases of the different pathogenic species of Streptococcus cleave the hinge of the alpha chain of human IgA1 only at one proline-threonine peptide bond. In order to study the importance of these amino acids for cleavage, several hinge mutant recombinant IgA1 antibodies were constructed. The mutations were found to be without major effect upon the structure or functional abilities of the antibodies. However, they had a major effect upon their sensitivity to cleavage by some of the IgA1 proteases. 相似文献
103.
The performance of fungal xylan-degrading enzyme preparations in elemental chlorine-free bleaching for Eucalyptus pulp 总被引:2,自引:0,他引:2
Medeiros RG Silva FG Salles BC Estelles RS Filho EX 《Journal of industrial microbiology & biotechnology》2002,28(4):204-206
Cellulase-free xylan-degrading enzyme preparations from Acrophialophora nainiana, Humicola grisea var. thermoidea and two Trichoderma harzianum strains were used as bleaching agents for Eucalyptus kraft pulp, prior to a chlorine dioxide and alkaline bleaching sequence. In comparison to the control sequence (performed
without xylanase pretreatment), the sequence incorporating enzyme treatment was more effective. Removal of residual lignin
was indicated by a reduction in kappa number. Overall, enzyme preparations from T. harzianum were marginally more effective in reducing pulp viscosity and chlorine chemical consumption and improving the brightness
of the kraft pulp. However, the highest reduction in pulp viscosity was mediated by the xylanase preparation from A. nainiana. Xylanase pretreatment compares very favorably with that of chemical pulping. Journal of Industrial Microbiology & Biotechnology (2002) 28, 204–206 DOI: 10.1038/sj/jim/7000227
Received 27 April 2001/ Accepted in revised form 03 November 2001 相似文献
104.
Summary Light- and electron-microscopic autoradiographic studies of pituitaries of the molly Poecilia latipinna, after their incubation with tritiated serotonin, revealed the presence of labelled cells in the proximal pars distalis, together with cell processes or nerve fibres throughout all regions of the gland except the prolactin cell zone. The serotonincon-centrating cells and most of the fibres contained small dense-cored vesicles, but some labelled fibres contained larger granules similar in ultrastructure to those of vasotocinergic fibres.This work was supported by a SERC studentship to DJG and SERC grant GR/6379-06 to Professor J.N. Ball 相似文献
105.
106.
Control of endometrial oxytocin receptor and uterine response to oxytocin by progesterone and oestradiol in the ewe 总被引:1,自引:0,他引:1
The effects of administration of progesterone and oestradiol on ovine endometrial oxytocin receptor concentrations and plasma concentrations of 13,14-dihydro-15-keto prostaglandin F-2 alpha (PGFM) after oxytocin treatment were determined in ovariectomized ewes. Ewes received progestagen pre-treatment, progesterone and/or oestradiol in 11 different treatment schedules. Progestagen pre-treatment decreased oxytocin receptor concentrations in endometrium from ewes treated subsequently with either progesterone for 5 days or progesterone for 5 days plus oestradiol on Days 4 and 5 of progesterone treatment. Oestradiol increased endometrial oxytocin receptor concentrations when administered on Days 4 and 5 of 5 days progesterone treatment. Progestagen pre-treatment followed by progesterone treatment for 12 days caused a large increase in oxytocin receptors and no further increase occurred when ewes were given oestradiol on Days 11 and 12, or when progesterone was withdrawn on Days 11 and 12, or these two treatments were combined. Oxytocin administration caused an increase in plasma PGFM concentrations in ewes which did not receive progestagen pre-treatment, and subsequently received progesterone treatment for 5 days and oestradiol treatment on Days 4 and 5 of progesterone treatment. Similarly treated ewes which received progestagen pre-treatment did not respond to oxytocin. Oxytocin administration also increased plasma PGFM concentrations in ewes which received progestagen pre-treatment followed by progesterone treatment for 12 days, progesterone treatment for 12 days plus oestradiol on Day 11 and 12 of progesterone treatment, progesterone withdrawal on Day 11 and 12, or progesterone withdrawal and oestradiol treatment combined. The results indicate that (1) progesterone pre-treatment affects oxytocin receptor concentrations in the endometrium and uterine responsiveness to oxytocin and (2) progesterone treatment alone for 12 days after a treatment which mimics a previous luteal phase and oestrus is sufficient to induce oxytocin receptors and increase oxytocin-induced PGF release. These results emphasize the importance of progesterone and provide information which can be used to form an hypothesis for control of luteolysis and oestrous cycle length in the ewe. 相似文献
107.
Eleven episodes of "meconium ileus equivalent" have been seen in six adults with cystic fibrosis of the pancreas. Three patients were initially treated surgically; one died and the other two developed serious postoperative chest infections. Six episodes were successfully treated medically with acetylcysteine orally and by enema, nasogastric suction, and intravenous fluids. Operation should be avoided if possible, and maintenance treatment with acetylcysteine may be necessary to prevent relapse. 相似文献
108.
109.
Ovarian granulosa cells grown on glass coverslips were split by a "sandwich" technique. Using this technique we describe a complex filamentous network in the cytoplasm of cultured granulosa cells that was composed of a branching and anastomosing lattice of filaments 20-40 nm in diameter. Since filament identification is impossible on the basis of size, split cells were decorated with S-1 fragments of rabbit skeletal muscle myosin. It was readily apparent that the major constituent of the filamentous lattice was actin. Actin was organized in large bundles in which individual filaments were longitudinally aligned. Actin was also observed organized in a loose network throughout the remainder of the cytoplasm. Actin appeared to be intimately associated with organelle and plasma membranes. Coated pits were also a site of actin-filament interaction. Filament polarity was generally away from the membrane with which filaments were associated. 相似文献
110.
D Junglee A Penketh A Katrak M E Hodson J C Batten P Dandona 《BMJ (Clinical research ed.)》1983,286(6379):1693-1694
Patients with cystic fibrosis have been found to have abnormal serum concentrations of immunoreactive trypsin and abnormal activities of pancreatic isoamylase. A study was undertaken to discover whether activity of pancreatic lipase is also altered in cystic fibrosis. Serum from 23 patients with cystic fibrosis was assayed for immunoreactive trypsin and pancreatic lipase. Median serum pancreatic lipase activity was significantly lower in patients with cystic fibrosis than in controls, as was immunoreactive trypsin concentration (p less than 0.0001). Some patients had supranormal lipase concentrations but these were not always associated with absence of malabsorption. Serum pancreatic lipase activity is considerably changed in cystic fibrosis. 相似文献