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101.
We employed a genetic approach to study protein glycosylation in the
procyclic form of the parasite Trypanosoma brucei. Two different mutant
parasites, ConA 1-1 and ConA 4-1, were isolated from mutagenized cultures
by selecting cells which resisted killing or agglutination by concanavalin
A. Both mutant cells show reduced concanavalin A binding. However, the
mutants have different phenotypes, as indicated by the fact that ConA 1-1
binds to wheat germ agglutinin but ConA 4-1 and wild type do not. A blot
probed with concanavalin A revealed that many proteins in both mutants lost
the ability to bind this lectin, and the blots resembled one of wild type
membrane proteins treated with PNGase F. This finding suggested that the
mutants had altered asparagine- linked glycosylation. This conclusion was
confirmed by studies on a flagellar protein (Fla1) and procyclic acidic
repetitive protein (PARP). Structural analysis indicated that the N- glycan
of wild type PARP is exclusively Man5GlcNAc2 whereas that in both mutants
is predominantly a hybrid type with a terminal N- acetyllactosamine. The
occupancy of the PARP glycosylation site in ConA 4-1 was much lower than
that in ConA 1-1. These mutants will be useful for studying trypanosome
glycosylation mechanisms and function.
相似文献
102.
Fermentation of cellulose by Ruminococcus flavefaciens in the presence and absence of Methanobacterium ruminantium 总被引:2,自引:0,他引:2
The anaerobic cellulolytic rumen bacterium Ruminococcus flavefaciens normally produces succinic acid as a major fermentation product together with acetic and formic acids, H2, and CO2. When grown on cellulose and in the presence of the methanogenic rumen bacterium Methanobacterium ruminantium, acetate was the major fermentation product; succinate was formed in small amounts; little formate was detected; H2 did not accumulate; and large amounts of CH4 were formed. M. ruminantium depends for growth on the reduction of CO2 to CH4 by H2, which it can obtain directly or by producing H2 and CO2 from formate. In mixed culture, the methanobacterium utilized the H2 and possibly the formate produced by the ruminococcus and in so doing stimulated the flow of electrons generated during glycolysis by the ruminococcus toward H2 formation and away from formation of succinate. This type of interaction may be of significance in determining the flow of cellulose carbon to the normal rumen fermentation products. 相似文献
103.
Cell wall polymers and phage lysis of Lactobacillus plantarum 总被引:2,自引:0,他引:2
104.
The effects of O2 tension on force in precontracted isolated pulmonary arterial smooth muscle from calf lungs was characterized to investigate the mechanism of O2 tension sensing. These arteries display a decrease in force with increasing O2 tension that is antagonized via inhibition of soluble guanylate cyclase activation by 10 microM methylene blue or inactivation of catalase by pretreatment with 50 mM 3-amino-1,2,4-triazole for 30 min. O2 tension-dependent relaxation is associated with an increase in intracellular H2O2 metabolism through catalase (detected as the peroxide-dependent inactivation of tissue catalase activity by aminotriazole) and cyclic guanosine 5'-monophosphate (cGMP), known mediators of relaxation in calf pulmonary arteries. Thus a recently reconstructed mechanism of activation of soluble guanylate cyclase involving the metabolism of H2O2 by catalase appears to function as an O2 tension sensor in pulmonary arteries. 相似文献
105.
106.
Mingone CJ Gupte SA Chow JL Ahmad M Abraham NG Wolin MS 《American journal of physiology. Lung cellular and molecular physiology》2006,291(3):L337-L344
Protoporphyrin IX is an activator of soluble guanylate cyclase (sGC), but its role as an endogenous regulator of vascular function through cGMP has not been previously reported. In this study we examined whether the heme precursor delta-aminolevulinic acid (ALA) could regulate vascular force through promoting protoporphyrin IX-elicited activation of sGC. Exposure of endothelium-denuded bovine pulmonary arteries (BPA) in organoid culture to increasing concentrations of the heme precursor ALA caused a concentration-dependent increase in BPA epifluorescence, consistent with increased tissue protoporphyrin IX levels, associated with decreased force generation to increasing concentrations of serotonin. The force-depressing actions of 0.1 mM ALA were associated with increased cGMP-associated vasodilator-stimulated phosphoprotein (VASP) phosphorylation and increased sGC activity in homogenates of BPA cultured with ALA. Increasing iron availability with 0.1 mM FeSO(4) inhibited the decrease in contraction to serotonin and increase in sGC activity caused by ALA, associated with decreased protoporphyrin IX and increased heme. Chelating endogenous iron with 0.1 mM deferoxamine increased the detection of protoporphyrin IX and force depressing activity of 10 microM ALA. The inhibition of sGC activation with the heme oxidant 10 muM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) attenuated the force depressing actions of an NO donor without altering the actions of ALA. Thus control of endogenous formation of protoporphyrin IX from ALA by the availability of iron is potentially a novel physiological mechanism of controlling vascular function through regulating the activity of sGC. 相似文献
107.
The activities of populations in complex anaerobic microbial communities that perform complete bioconversion of organic matter to CH4 and CO2 are reviewed. Species of eubacteria produce acetate, H2, and CO2 from organic substrates, and methanogenic species of archaebacteria transform the acetate, H2, and CO2 to CH4. The characteristics and activities of the methanogenic bacteria are described. The impact of the use of H2 by methanogens on the fermentations that produce acetate, H2, and CO2 and the importance of syntrophy in complete bioconversion are discussed. 相似文献
108.
A variety of cytochemical techniques were used to demonstrate how crustacean lipovitellin accumulates within the egg. It was found that a protein serologically identical to the lipovitellin of yolk spheres was present in the hemolymph of vitellogenic crustaceans, but was absent from the hemolymph of males and immature females.In the three crustacean species studied (Uca pugilator, Cambarus clarkii, and Libinia emarginata), pinocytosis of fluorescein-conjugated lipovitellin and trypan blue occurred only during those periods when oocytes were accumulating yolk.It may be concluded from the present studies that yolk spheres develop in crustacean eggs primarily through micropinocytotic uptake of lipovitellin from the hemolymph, although other oocyte proteins appear to be made in the oocyte. 相似文献
109.
Modulation of cGMP by human HO-1 retrovirus gene transfer in pulmonary microvessel endothelial cells
Abraham NG Quan S Mieyal PA Yang L Burke-Wolin T Mingone CJ Goodman AI Nasjletti A Wolin MS 《American journal of physiology. Lung cellular and molecular physiology》2002,283(5):L1117-L1124
Carbon monoxide (CO) stimulates guanylate cyclase (GC) and increases guanosine 3',5'-cyclic monophosphate (cGMP) levels. We transfected rat-lung pulmonary endothelial cells with a retrovirus-mediated human heme oxygenase (hHO)-1 gene. Pulmonary cells that expressed hHO-1 exhibited a fourfold increase in HO activity associated with decreases in the steady-state levels of heme and cGMP without changes in soluble GC (sGC) and endothelial nitric oxide synthase (NOS) proteins or basal nitrite production. Heme elicited significant increases in CO production and intracellular cGMP levels in both pulmonary endothelial and pulmonary hHO-1-expressing cells. N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NOS, significantly decreased cGMP levels in heme-treated pulmonary endothelial cells but not heme-treated hHO-1-expressing cells. In the presence of exogenous heme, CO and cGMP levels in hHO-1-expressing cells exceeded the corresponding levels in pulmonary endothelial cells. Acute exposure of endothelial cells to SnCl2, which is an inducer of HO-1, increased cGMP levels, whereas chronic exposure decreased heme and cGMP levels. These results indicate that prolonged overexpression of HO-1 ultimately decreases sGC activity by limiting the availability of cellular heme. Heme activates sGC and enhances cGMP levels via a mechanism that is largely insensitive to NOS inhibition. 相似文献
110.
Separation of the primary dehydrogenase from the cytochromes of the nicotinamide adenine dinucleotide (reduced form) oxidase of Bacillus megaterium 总被引:1,自引:1,他引:1 下载免费PDF全文
A selective extraction procedure was developed for sequentially extracting a fraction containing the primary dehydrogenase and a fraction containing the cytochromes of the nicotinamide adenine dinucleotide (reduced form) (NADH) oxidase of Bacillus megaterium KM membranes. The primary dehydrogenase (NADH-2,6-dichlorophenolindophenol oxidoreductase) activity was extracted from sonically treated membranes with 0.4% sodium deoxycholate for 30 min at 4 C. The insoluble residue was extracted with 0.4% sodium deoxycholate in 1 m KCl for 30 min at 25 C. A combination of the two extracts and dilution in Mg(2+) gave good recovery of the original membrane NADH oxidase activity. The primary dehydrogenase fraction contained 41% of the membrane protein, no cytochromes, flavine adenine dinucleotide as the sole acid-extractable flavine, and most of the membrane ribonucleic acid (RNA). The cytochrome-containing fraction had 16% of the membrane protein, 61% of the membrane cytochrome with the same relative amounts of cytochromes a and b as the original membrane, no acid-extractable flavine, little RNA, and no oxidoreductase activity. The oxidoreductase fraction remained soluble after removal of deoxycholate whereas the cytochrome fraction became insoluble after removal of deoxycholate-KCl, but the precipitated fraction could be redissolved in 0.4% sodium deoxycholate. Treatment of both fractions with ribonuclease to destroy all of the RNA present did not affect the ability of the fractions to recombine into a functional oxidase unit. Treatment of either fraction with phospholipase A prevented restoration of a functional oxidase when the oxidoreductase and cytochrome fractions were treated in solution, but no affect on restoration of oxidase was observed when the phospholipase A treatment was carried out with the soluble oxidoreductase fraction and the insoluble cytochrome fraction. 相似文献