共查询到20条相似文献,搜索用时 15 毫秒
1.
The structure of bovine lysosomal alpha-mannosidase suggests a novel mechanism for low-pH activation
Heikinheimo P Helland R Leiros HK Leiros I Karlsen S Evjen G Ravelli R Schoehn G Ruigrok R Tollersrud OK McSweeney S Hough E 《Journal of molecular biology》2003,327(3):631-644
Lysosomal alpha-mannosidase (LAM: EC 3.2.1.24) belongs to the sequence-based glycoside hydrolase family 38 (GH38). Two other mammalian GH38 members, Golgi alpha-mannosidase II (GIIAM) and cytosolic alpha-mannosidase, are expressed in all tissues. In humans, cattle, cat and guinea pig, lack of lysosomal alpha-mannosidase activity causes the autosomal recessive disease alpha-mannosidosis. Here, we describe the three-dimensional structure of bovine lysosomal alpha-mannosidase (bLAM) at 2.7A resolution and confirm the solution state dimer by electron microscopy. We present the first structure of a mammalian GH38 enzyme that offers indications for the signal areas for mannose phosphorylation, suggests a previously undetected mechanism of low-pH activation and provides a template for further biochemical studies of the family 38 glycoside hydrolases as well as lysosomal transport. Furthermore, it provides a basis for understanding the human form of alpha-mannosidosis at the atomic level. The atomic coordinates and structure factors have been deposited in the Protein Data Bank (accession codes 1o7d and r1o7dsf). 相似文献
2.
Pseudomonas cichorii strainS, isolated by soil enrichment technique, utilized santonin as the sole source of carbon, forming chromatographically destinguishable
transformation products. One of the intermediary transformation products was identified as 1,2-dihydro α-santonin. 相似文献
3.
4.
5.
6.
P G Pentchev R O Brady S R Hibbert A E Gal D Shapiro 《The Journal of biological chemistry》1973,248(15):5256-5261
7.
Takayoshi Tokiwa Hidekazu Nakabayashi Masahiro Miyazaki Jiro Sato 《In vitro cellular & developmental biology. Plant》1979,15(6):393-400
Summary A high frequency of diploid and near-diploid clones were developed from cell lines derived from adult and newborn rat liver
using micropipettes. There were some differences in morphology, biochemical properties and growth rate between clones. Cloned
cells had low levels of tyrosine transaminase activity, glucose-6-phosphatase activity and albumin content. A diploid clone
and a pseudodiploid clone derived from adult rat liver cell line were positive for α-fetoprotein.
This work was supported by a grant for cancer research from the Japanese Ministry of Education. 相似文献
8.
9.
Janice Yang Chou Patricia E. Hugunin Toshiaki Mano 《In vitro cellular & developmental biology. Plant》1983,19(7):571-575
Summary The synthesis of human chorionic gonadotropin (HCG), the subunit of HCG (HCGα), and pregnancy-specific β1-glycoprotein (PSβG) was studied in temperature senstive (ts), simian virus 40 (SV40)tsA mutant-transformed human first trimenster placental (SPA255-26) cells. Retinoic acid increased the production of HCG and PSβG but inhibited the production of HCGα in these cells. Passage
ofSPA255-26 placental cells in medium containing retinoic acid induced a stable altered phenotype characterized by elevated levels of
HCG and PSβG and a reduced level of HCGα. The retinoic acid induced phenotypic changes in these placental cells were reversible;
removal of retinoic acid immediately decreased the production of HCG and PSβG while increasing the production of HCGα. The
ratio of HCG to HCGα in controlSPA255-26 cells was approximately 0.1; this ratio in creased to 4.8 in cells maintained in medium containing retinoic acid. Similarly,
the HCG-to-HCGα ratio increased in choriocarcinoma cells maintained in retinoic acid containing medium. Our data suggest that
retinoic acid may be needed to maintain a blanced production of HCG, HCGα, and PSβG in placental cells in vitro. Retinoic
acid may also play a role in modulating placental protein production during pregnancy. 相似文献
10.
The binding of several radioactive steroids was examined in mouse placental tissue, using Sephadex chromatography to separate the labelled steroid complex from free steroids. Binding was exhibited by cortisol, corticosterone and progesterone, but not cortisone. Cortexolone, an antiglucocorticoid, was tested in the system and found to reduce the binding of the active steroids. The displacement of labelled corticosterone by addition of unlabelled steroids was also examined. Preliminary characterization of the corticosterone receptor using hydrolytic enzymes suggested a protein nature on the basis of degradation by pronase but not by nucleases. 相似文献
11.
Kinouchi T Nishio H Nishiuchi Y Tsunemi M Takada K Hamamoto T Kagawa Y Fujii N 《Amino acids》2007,32(1):79-85
Summary. The accumulation of D-isomers of aspartic acid (D-Asp) in proteins during aging has been implicated in the pathogenesis of Alzheimer’s disease (AD), cataracts and arteriosclerosis.
Here, we identified a specific lactacystin-sensitive endopeptidase that cleaves the D-Asp-containing protein and named it D-aspartyl endopeptidase (DAEP). DAEP has a multi-complex structure (MW: 600 kDa) and is localized in the inner mitochondrial
membrane. However, DAEP activity was not detected in E. coli, S. cerevisiae, and C. elegans. A specific inhibitor for DAEP, i-DAEP: (benzoyl-L-Arg-L-His-[D-Asp]-CH2Cl; MW: 563.01), was newly synthesized and inhibited DAEP activity (IC50, 3 μM), a factor of ten greater than lactacystin on DAEP. On the other hand, i-DAEP did not inhibit either the 20S or 26S
proteasome. And we identified succinate dehydrogenase and glutamate dehydrogenase 1 as components of DAEP by affinity label
using biotinylated i-DAEP. In the long life span of mammals, DAEP may serve as a scavenger against accumulation of racemized
proteins in aging. Insights into DAEP will provide the foundation for developing treatments of diseases, such as AD, in which
accumulation of D-Asp-containing proteins are implicated. 相似文献
12.
Sergei Vyalov Alexis Desmoulière Giulio Gabbiani 《Virchows Archiv. B, Cell pathology including molecular pathology》1993,63(1):231-239
We have studied the formation of granulation tissue around osmotic minipumps delivering granulocyte macrophage-colony stimulating
factor (GM-CSF) chronologically in the rat using electron microscopy and immunohistochemistry at the light and electron microscopic
levels, with specific antibodies against α-smooth muscle (SM) actin and rat macrophages. At 2 and 3 days after pump implantation,
GM-CSF application produced an extensive inflammatory reaction characterized by edema and the accumulation of polymorphonuclear
cells and macrophages. Gradually, polymorphonuclear cells decreased in number and macrophages became arranged in large clusters.
The expression of α-SM actin in fibroblastic cells of the granulation tissue started from the 4th day after pump implantation
and progressed up to the 7th day. Double immunofluorescence staining showed macrophage clusters in relation to α-SM actinrich
fibroblastic cells. Electron microscopic examination confirmed that the fibroblasts containing α-SM actinpositive stress fibers
were found initially in close proximity to clustered macrophages. The delivery of plateletderived growth factor (PDGF) and
tumor necrosis factor-α (TNF-α) by the osmotic minipump induced an accumulation of macrophages, but in a much smaller number
compared with those seen after GM-CSF application; these macrophages were never assembled in clusters and, furthermore, TNF-α
and PDGF did not stimulate α-SM actin expression in fibroblastic cells. Our results suggest that after GM-CSF administration,
the cluster-like accumulation of macrophages plays an important role in stimulating α-SM actin expression in myofibroblasts.
Our results may be relevant to the understanding of the processes leading to granulation tissue formation in this and other
experimental models. 相似文献
13.
Two isoperoxidases (Af and Cn) from the medium of tobacco tissue suspension culture WR-132 grown in darkness have been purified to apparent homogeneity and partially characterized. Cn and Af have MWs of ca 30 000 and 54 000, respectively. Af has ca 5.1% carbohydrate, but none could be detected in Cn. Both isoperoxidases appear to follow simple Michaelis-Menten kinetics with respect to guaiacol as the substrate. The Kms for guaiacol are 4 and 13.3 mM for Af and Cn, respectively, while both isoperoxidases have a pH optimum at 6.5. Cn, is dissimilar to other isoperoxidases from tobacco tissue cultures, but Af is very similar to isoperoxidase A3 from W-38 tobacco tissue culture. 相似文献
14.
Two acyl-CoA-binding-protein (ACBP) isoforms were isolated from proembryogenic masses of Digitalis lanata Ehrh. by column chromatography and preparative HPLC. The ACBPs had molecular masses of 9926 and 9997 Da, respectively. Partial
sequence data indicated high similarity to each other and to ACBPs of other plant species such as Ricinus communis, Brassica napus and Arabidopsis thaliana. The isolated ACBPs bound palmitoyl-CoA with high affinity as determined by isoelectric-point shift.
Received: 29 May 1999 / Accepted: 28 August 1999 相似文献
15.
Imazawa Y Imai K Fukushima A Hisatake K Muramatsu M Nogi Y 《Molecular & general genetics : MGG》1999,262(4-5):749-757
Eukaryotic RNA polymerases I and III share two distinct α-related subunits that show limited homology to the α subunit of
Escherichia coli RNA polymerase, which forms a homodimer to nucleate the assembly of prokaryotic RNA polymerase. To gain insight into the
functions of α-related subunits in eukaryotes, we have previously identified the α-related small subunit RPA17 of RNA polymerase
I (and III) in Schizosaccharomyces pombe, and have shown that it is a functional homolog of Saccharomyces cerevisiae AC19. In an extension of that study, we have now isolated and characterized rpa42
+, which encodes the α-related large subunit RPA42 of S. pombe RNA polymerase I, by virtue of the fact that its product interacts with RPA17 in the yeast two-hybrid system. We have found
that rpa42
+ encodes a polypeptide with an apparent molecular mass of 42 kDa, which shows 58% identity to the AC40 subunit shared by RNA
polymerases I and III in S. cerevisiae. Furthermore, we have shown that rpa42
+ complements a temperature-sensitive mutation in RPC40 the gene that encodes AC40 in S. cerevisiae and which is essential for cell growth. Finally, we have shown that neither RPA42 nor RPA17 can self-associate. These results
provide evidence that the two distinct α-related subunits, RPA42 and RPA17, of RNA polymerases I and III are functionally
conserved between S. pombe and S. cerevisiae, and suggest that heterodimer formation between them is essential for the assembly of RNA polymerases I and III in eukaryotes.
Received: 20 April 1999 / Accepted: 26 July 1999 相似文献
16.
ATPase activity was studied in calli from olive (Olea europaea L.) petioles cultured in media modified in their auxin/cytokinin
ratio in order to induce different morphogenetic responses. Addition of 0.54 μM α-naphthaleneacetic acid (NAA) or 14 μM zeatin
(ZEA) did not induce any morphogenesis in calli and proton pump activity in vivo was very low, while calli produced roots
at 27 or 11 μM NAA + 0.28 μM ZEA and possessed clearly detectable proton pump activity. ATPase activity associated with microsomes
isolated by differential centrifugation from different callus cultures had the same pH optimum and similar sensitivity toward
nitrate and azide. However, microsomes isolated from non-morphogenetic calli had higher specific ATPase activity which was
very poorly (6 %) inhibited by vanadate. Also, the fractionation of these microsomes on a continuous sucrose gradient showed
two peaks of ATPase activity, the more pronounced one co-purifying with the Golg i marker enzyme, Triton-stimulated UDPase
activity, suggesting thus the presence of very high ATPase activity in Golgi secretory vesicles. On the contrary, ATPase activity
of microsomes from calli producing roots was more sensitive to vanadate (30 - 40 % inhibition). Furthermore, the component
of ATPase activity attributable to Golgi secretory vesicles was less abundant.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Improved purification of potato tuber invertase was achieved by utilizing a form of affinity chromatography between the enzyme and Concanavalin A (Con A) bound to Sepharose. Twenty-fold increases in specific activity were routinely obtained with this step and the enzyme was purified 190-fold over that found in the crude homogenate. The Con A-Sepharose chromatography step gave a greater purification than any other step in the invertase isolation procedure. There was up to 170% recovery of the activity loaded onto the column. α-Methyl-d-mannoside, sucrose, d-glucose and d-fructose eluted the enzyme from the Con A-Sepharose column with similar recoveries, although the volume of eluent required varied with the sugar. This unusually high recovery of invertase activity was obtained with some batches of tubers but not with others. There was evidence to suggest that the high recovery, or activation, may be due to the release of an inhibitor from the enzyme in the presence of Con A-Sepharose. Adsorption of invertase to Con A-Sepharose could be eliminated by incubation of the enzyme with α-mannosidase and β-glucosidase, indicating that potato tuber invertase is a glycoprotein. Proteinaceous inhibitor purification was improved by treatment of the tuber extract at low pH. 相似文献
18.
Aleksandra Olma Dirk Tourwé 《International journal of peptide research and therapeutics》2000,7(2):93-96
Summary Novel endomorphin-2 analogs containing the unusual amphiphilic amino acid (R)- and (S)-α-hydroxymethyltyrosine in position 1 and (R)- and (S)-α-hydroxymethylphenylalanine in the positions 3 and 4 were synthesized via the solid-phase method. The binding characteristics
of the synthetic analogs may suggest that α-hydroxymethyl substitution of amino acid residues influences the conformation
of a peptide much more than simply increasing the local amphiphilic character of the peptide. 相似文献
19.
Isolation and characterization of natural products from plant tissue cultures of Maytenus buchananii
James P. Kutney Michael H. Beale Phillip J. Salisbury Kenneth L. Stuart Brian R. Worth Phillip M. Townsley William T. Chalmers Kristina Nilsson Giullo G. Jacoli 《Phytochemistry》1981,20(4):653-657
Explants of Maytenus buchananii were induced to form a callus aid subsequently to form suspension cultures on a wide variety of media. Culture extracts showed cytotoxic activity, but examination by TLC did not indicate the presence of maytansine. Isolation of natural products from a large scale suspension culture led to the identification of polpunonic acid, sitosterol and the cytotoxic triterpene quinone-methides, tingenone and 22β-hydroxytingenone. Possible biosynthetic relationships of these and other triterpene quinone-methides are discussed. 相似文献
20.
Yamasaki M Nishida E Nou S Tachibana H Yamada K 《In vitro cellular & developmental biology. Animal》2005,41(7):239-244
Summary This study was performed to evaluate the isomer-specific cytotoxic effects of conjugated linoleic acid (CLA) on rat hepatoma
dRLh-84 cells in vitro. A 10trans,12cis (10t,12c)-CLA showed a strong cytotoxic effect on dRLh-84 cells in culture, whereas no such effect was observed with 9cis,11trans (9c,11t)-CLA or linoleic acid. The optimum concentration for induction of cytotoxity by 10t,12c-CLA was 5 to 10 μM, but the effect was alleviated at higher concentrations. Coincubation with oleic or palmitoleic acid and 10t,12c-CLA cancelled the cytotoxic effect, but other major saturated or polyunsaturated fatty acids and eraidic acid did not interfere
with 10t,12c-CLA-induced cytotoxity. The cytotoxic effect was also alleviated by α-tocopherol (α-toc) and α-tocotrienol but not by any
other antioxidant regent examined. Significant cytotoxity of 10t,12c-CLA was detected after only a 15-min incubation, and the most noticeable effect was seen after 3 h. After incubation with
10t,12c-CLA at 10 μM, an additional 90 μM, an additional 90 μM of 10t,12c-CLA or 100 μM of α-toc was also able to alleviate the cytotoxity. When cells were treated with 10 μM 10t,12c-CLA for more than 48 h, treatment with additional CLA or α-toc could not prevent cell death. 相似文献