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211.
The C. elegans PUF and FBF proteins regulate various aspects of germline development by selectively binding to the 3' untranslated region of their target mRNAs and repressing translation. Here, we show that puf-8, fbf-1 and fbf-2 also act in the soma where they negatively regulate vulvaI development. Loss-of-function mutations in puf-8 cause ectopic vulval differentiation when combined with mutations in negative regulators of the EGFR/RAS/MAPK pathway and suppress the vulvaless phenotype caused by mutations that reduce EGFR/RAS/MAPK signalling. PUF-8 acts cell-autonomously in the vulval cells to limit their temporal competence to respond to the extrinsic patterning signals. fbf-1 and fbf-2, however, redundantly inhibit primary vulval cell fate specification in two distinct pathways acting in the soma and in the germline. The FBFs thereby ensure that the inductive signal selects only one vulval precursor cell for the primary cell fate. Thus, translational repressors regulate various aspects of vulval cell fate specification, and they may play a conserved role in modulating signal transduction during animal development. 相似文献
212.
During vermicomposting of coconut leaves by the earthworm Eudrilus sp., Oryctes rhinoceros L. (rhinoceros beetle), an insect pest of palms, was found to breed in the decomposing organic material. Metarhizium anisopliae var. major was tried as a biocontrol agent for management of this pest. The effect of pathogen at spore loads of 10(3), 10(4) and 10(5) per 10 g of substrate was tested in laboratory on Eudrilus sp. kept with O. rhinoceros grubs and on Eudrilus sp. alone for the pathogenic capability of the fungus on the pest and its possible toxicity towards the vermin. The efficacy of the entomopathogen was also tested in the field in vermicomposting tanks. In laboratory bioassay, 100% mycosis of O. rhinoceros grubs could be obtained while the entomopathogen had no toxic effect on the earthworms. There was a positive change in the number and weight of the earthworms on treatment with M. anisopliae. In the field, application of M. anisopliae reduced O. rhinoceros grubs in the vermicomposting tanks upto an extent of 72%. In conclusion, M. anisopliae could effectively control O. rhinoceros in vermicomposting sites and was non-hazardous to the vermicomposting process as well as the Eudrilus sp. 相似文献
213.
Kumar VS Sharma VL Tiwari P Singh D Maikhuri JP Gupta G Singh MM 《Bioorganic & medicinal chemistry letters》2006,16(9):2509-2512
The study investigated spermicidal and antitrichomonas activities of selective serotonin reuptake inhibitor (SSRI) antidepressants with a view to generate new lead for development of dual-function spermicidal microbicides, which is an urgent global need. Fluoxetine, Sertraline, and Fluvoxamine exhibited both spermicidal and anti-STI (antitrichomonas) activities in vitro, whereas Paroxetine and Citalopram showed only the spermicidal activity. Fluoxetine exhibited better activity profile than the other antidepressant drugs with its spermicidal and antitrichomonas activities being comparable to that of the OTC contraceptive Nonoxynol-9. The non-detergent nature of Fluoxetine and a much lower spermicidal ED50 value (than N-9) may add considerably to its merit as a candidate for microbicidal contraceptive. Thus, the antidepressants exhibiting both spermicidal and antitrichomonas activities might provide useful lead for the development of novel, dual-function spermicidal contraceptives. 相似文献
214.
A. hydrophila, a ubiquitous gram-negative bacterium present in aquatic environments, has been implicated in illness in humans, fish and amphibians.
Lipopolysaccharides (LPS), a surface component of the outer membrane, are one of the main virulent factors of gram-negative bacteria.
UDP-galactose 4-epimerase (GalE) catalyses the last step in the Leloir pathway of galactose metabolism and provides precursor for the biosynthesis
of extracellular LPS and capsule. Due to its key role in LPS biosynthesis, it is a potential drug target. The present study describes cloning, sequence
analysis and prediction of three dimensional structure of the deduced amino acid sequence of the galE of A. hydrophila AH17. The cloned galE
consists of the putative promoter-operator region, and an open reading frame of 338 amino acid residues. Sequence alignment and predicted 3Dstructure
revealed that the GalE of A. hydrophila consists of the signature sequences of the epimerase super family. The present study reports the
molecular modeling / 3D-structure prediction of GalE of A. hydrophila. Further, the potential regions of the enzyme that can be targeted for drug
design are identified. 相似文献
215.
Kulandaivelu S. Vetrivel Xavier Meckler Ying Chen Phuong D. Nguyen Nabil G. Seidah Robert Vassar Philip C. Wong Masaki Fukata Maria Z. Kounnas Gopal Thinakaran 《The Journal of biological chemistry》2009,284(6):3793-3803
Alzheimer disease β-amyloid (Aβ) peptides are generated via
sequential proteolysis of amyloid precursor protein (APP) by BACE1 and
γ-secretase. A subset of BACE1 localizes to cholesterol-rich membrane
microdomains, termed lipid rafts. BACE1 processing in raft microdomains of
cultured cells and neurons was characterized in previous studies by disrupting
the integrity of lipid rafts by cholesterol depletion. These studies found
either inhibition or elevation of Aβ production depending on the extent
of cholesterol depletion, generating controversy. The intricate interplay
between cholesterol levels, APP trafficking, and BACE1 processing is not
clearly understood because cholesterol depletion has pleiotropic effects on
Golgi morphology, vesicular trafficking, and membrane bulk fluidity. In this
study, we used an alternate strategy to explore the function of BACE1 in
membrane microdomains without altering the cellular cholesterol level. We
demonstrate that BACE1 undergoes S-palmitoylation at four Cys
residues at the junction of transmembrane and cytosolic domains, and Ala
substitution at these four residues is sufficient to displace BACE1 from lipid
rafts. Analysis of wild type and mutant BACE1 expressed in BACE1 null
fibroblasts and neuroblastoma cells revealed that S-palmitoylation
neither contributes to protein stability nor subcellular localization of
BACE1. Surprisingly, non-raft localization of palmitoylation-deficient BACE1
did not have discernible influence on BACE1 processing of APP or secretion of
Aβ. These results indicate that post-translational
S-palmitoylation of BACE1 is not required for APP processing, and
that BACE1 can efficiently cleave APP in both raft and non-raft
microdomains.Alzheimer disease-associated β-amyloid
(Aβ)3 peptides
are derived from the sequential proteolysis of β-amyloid precursor
protein (APP) by β- and γ-secretases. The major β-secretase is
an aspartyl protease, termed BACE1 (β-site
APP-cleaving enzyme 1)
(1–4).
BACE1 cleaves APP within the extracellular domain of APP, generating the N
terminus of Aβ. In addition, BACE1 also cleaves to a lesser extent within
the Aβ domain between Tyr10 and Glu11
(β′-cleavage site). Processing of APP at these sites results in the
shedding/secretion of the large ectodomain (sAPPβ) and generating
membrane-tethered C-terminal fragments +1 and +11 (β-CTF)
(5). The multimeric
γ-secretase cleaves at multiple sites within the transmembrane domain of
β-CTF, generating C-terminal heterogeneous Aβ peptides (ranging in
length between 38 and 43 residues) that are secreted, as well as cytosolic APP
intracellular domains (6). In
addition to BACE1, APP can be cleaved by α-secretase within the Aβ
domain between Lys16 and Leu17, releasing sAPPα
and generating α-CTF. γ-Secretase cleavage of α-CTF
generates N-terminal truncated Aβ, termed p3.Genetic ablation of BACE1 completely abolishes Aβ production,
establishing BACE1 as the major neuronal enzyme responsible for initiating
amyloidogenic processing of APP
(4,
7). Interestingly, both the
expression and activity of BACE1 is specifically elevated in neurons adjacent
to senile plaques in brains of individuals with Alzheimer disease
(8). In the past few years
additional substrates of BACE1 have been identified that include APP
homologues APLP1 and APLP2 (9),
P-selectin glycoprotein ligand-1
(10), β-galactoside
α2,6-sialyltransferase
(11), low-density lipoprotein
receptor-related protein (12),
β-subunits of voltage-gated sodium channels
(13), and neuregulin-1
(14,
15), thus extending the
physiological function of BACE1 beyond Alzheimer disease pathogenesis.BACE1 is a type I transmembrane protein with a long extracellular domain
harboring a catalytic domain and a short cytoplasmic tail. BACE1 is
synthesized as a proenzyme, which undergoes post-translational modifications
that include removal of a pro-domain by a furin-like protease,
N-glycosylation, phosphorylation, S-palmitoylation, and
acetylation, during the transit in the secretory pathway
(16–20).
In non-neuronal cells the majority of BACE1 localizes to late Golgi/TGN and
endosomes at steady-state and a fraction of BACE1 also cycles between the cell
surface and endosomes (21).
The steady-state localization of BACE1 is consistent with the acidic pH
optimum of BACE1 in vitro, and BACE1 cleavage of APP is observed in
the Golgi apparatus, TGN, and endosomes
(22–25).
BACE1 endocytosis and recycling are mediated by the GGA family of adaptors
binding to a dileucine motif (496DISLL) in its cytoplasmic tail
(21,
26–31).
Phosphorylation at Ser498 within this motif modulates GGA-dependent
retrograde transport of BACE1 from endosomes to TGN
(21,
26–31).Over the years, a functional relationship between cellular cholesterol
level and Aβ production has been uncovered, raising the intriguing
possibility that cholesterol levels may determine the balance between
amyloidogenic and non-amyloidogenic processing of APP
(32–34).
Furthermore, several lines of evidence from in vitro and in
vivo studies indicate that cholesterol- and sphingolipid-rich membrane
microdomains, termed lipid rafts, might be the critical link between
cholesterol levels and amyloidogenic processing of APP. Lipid rafts function
in the trafficking of proteins in the secretory and endocytic pathways in
epithelial cells and neurons, and participate in a number of important
biological functions (35).
BACE1 undergoes S-palmitoylation
(19), a reversible
post-translational modification responsible for targeting a variety of
peripheral and integral membrane proteins to lipid rafts
(36). Indeed, a significant
fraction of BACE1 is localized in lipid raft microdomains in a
cholesterol-dependent manner, and addition of glycosylphosphatidylinositol
(GPI) anchor to target BACE1 exclusively to lipid rafts increases APP
processing at the β-cleavage site
(37,
38). Antibody-mediated
co-patching of cell surface APP and BACE1 has provided further evidence for
BACE1 processing of APP in raft microdomains
(33,
39). Components of the
γ-secretase complex also associate with detergent-resistant membrane
(DRM) fractions enriched in raft markers such as caveolin, flotillin, PrP, and
ganglioside GM1 (40). The
above findings suggest a model whereby APP is sequentially processed by BACE1
and γ-secretase in lipid rafts.Despite the accumulating evidence, cleavage of APP by BACE1 in non-raft
membrane regions cannot be unambiguously ruled out because of the paucity of
full-length APP (APP FL) and BACE1 in DRM isolated from adult brain and
cultured cells (41). Moreover,
it was recently reported that moderate reduction of cholesterol (<25%)
displaces BACE1 from raft domains, and increases BACE1 processing by promoting
the membrane proximity of BACE1 and APP in non-raft domains
(34). Nevertheless, this study
also found that BACE1 processing of APP is inhibited with further loss of
cholesterol (>35%), consistent with earlier studies
(32,
33). Nevertheless, given the
pleiotropic effects of cholesterol depletion on membrane properties and
vesicular trafficking of secretory and endocytic proteins
(42–47),
unequivocal conclusions regarding BACE1 processing of APP in lipid rafts
cannot be reached based on cholesterol depletion studies.In this study, we explored the function of BACE1 in lipid raft microdomains
without manipulating cellular cholesterol levels. In addition to the
previously reported S-palmitoylation sites
(Cys478/Cys482/Cys485) within the cytosolic
tail of BACE1 (19), we have
identified a fourth site (Cys474) within the transmembrane domain
of BACE1 that undergoes S-palmitoylation. A BACE1 mutant with Ala
substitution of all four Cys residues (BACE1-4C/A) fails to associate with DRM
in cultured cells, but is not otherwise different from wtBACE1 in terms of
protein stability, maturation, or subcellular localization. Surprisingly, APP
processing and Aβ generation were unaffected in cells stably expressing
the BACE1-4C/A mutant. Finally, we observed an increase in the levels of APP
CTFs in detergent-soluble fractions of BACE1-4C/A as compared with wtBACE1
cells. Thus, our data collectively indicate a non-obligatory role of
S-palmitoylation and lipid raft localization of BACE1 in
amyloidogenic processing of APP. 相似文献
216.
Prasert Laobusnanant Seung Hwan Lee Alfredo J. Anceno Gopal C. Ghosh Dong Jin Kim Bipin K. Pathak Oleg V. Shipin 《Bioprocess and biosystems engineering》2009,32(6):809-818
Biological N-removal treatment of piggery wastewater in the upflow anaerobic–anoxic–aerobic floating filter (UA3FF) bioreactor based on the concept of nitritation–denitritation was studied along with the changes in internal recycle ratio
and dissolved oxygen concentration (DO). Consecutive changes in the recirculation ratio between the anoxic and aerobic reactors
has resulted in abundance and composition shifts of N-cycling bacteria as well as other bacterial groups, reflecting different
survival strategies across (bio/physico)chemical milieu. The DO concentration was optimized to achieve nitritation in the
aerobic reactor and denitritation in the anoxic reactor. Optimal nitritation–denitritation (270 and 130 g NO2
−–N produced or reduced/m3 filter media/day) was obtained at DO of 1.0–1.5 mg/l, inter-reactor recirculation ratio of 1:1–2:1, HRT of 24 h, pH of 7.6 ± 0.3,
and temperature of 28 ± 4 °C. Since only well known nitrifying and denitrifying taxa were found, nitritation–denitritation
was likely carried out by these bacteria rather than the yet unidentified novel taxa. Archaeal nitrifiers recently discovered
to be important in the global N-cycle were not detected. 相似文献
217.
Cell cultures of Pueraria tuberosa were grown in vessels of different sizes and 2L stirred tank bioreactor containing modified MS medium with morphactin (0.1 mg l?1) and 2iP (5.0 mg l?1) and 20% inoculum. Stable growth and total isoflavonoid yield of 76.6 mg l?1 were recorded in the cultures during scale up. This was in concordance with the persistent yield of the individual isoflavonoids regardless of the vessel size. 相似文献
218.
219.
V. Sandhya Sk. Z. Ali B. Venkateswarlu Gopal Reddy Minakshi Grover 《Archives of microbiology》2010,192(10):867-876
In this study we isolated and screened drought tolerant Pseudomonas isolates from arid and semi arid crop production systems of India. Five isolates could tolerate osmotic stress up to −0.73 MPa
and possessed multiple PGP properties such as P-solubilization, production of phytohormones (IAA, GA and cytokinin), siderophores,
ammonia and HCN however under osmotic stress expression of PGP traits was low compared to non-stressed conditions. The strains
were identified as Pseudomonas
entomophila, Pseudomonas
stutzeri, Pseudomonas putida, Pseudomonas syringae and Pseudomonas monteilli respectively on the basis of 16S rRNA gene sequence analysis. Osmotic stress affected growth pattern of all the isolates
as indicated by increased mean generation time. An increase level of intracellular free amino acids, proline, total soluble
sugars and exopolysaccharides was observed under osmotic stress suggesting bacterial response to applied stress. Further,
strains GAP-P45 and GRFHYTP52 showing higher levels of EPS and osmolytes (amino acids and proline) accumulation under stress
as compared to non-stress conditions, also exhibited higher expression of PGP traits under stress indicating a relationship
between stress response and expression of PGP traits. We conclude that isolation and screening of indigenous, stress adaptable
strains possessing PGP traits can be a method for selection of efficient stress tolerant PGPR strains. 相似文献
220.
Hameeda B Harini G Rupela OP Kumar Rao JV Reddy G 《Indian journal of microbiology》2010,50(4):419-424
Two hundred and seven bacteria were isolated from composts and macrofauna and screened for plant growth promoting and antagonistic
traits. Seven of the 207 isolates showed antagonistic activity against Sclerotium rolfsii in plate culture. Inhibition of S. rolfsii by the bacterial isolates ranged between 61 and 84%. Two of the seven isolates were Bacillus sp. and rest belonged to Pseudomonas sp. Two isolates, Pseudomonas sp. CDB 35 and Pseudomonas sp. BWB 21 was compatible with chickpea Rhizobium sp. IC 59 and IC 76 in plate culture conditions. Increase in plant biomass (dry weight) ranged between 18 and 30% on application
of these bacteria by seed coating and seed priming methods. However, by seed-priming there was an increase in plant biomass
by 5–7% compared to seed coating. Number of nodules and the nodule weight was similar by both seed coating and seed priming
methods. Disease incidence was reduced up to 47% in treatments where captan (fungicide) or antagonistic Pseudomonas sp. CDB 35 was applied. Increase in shoot weight was 36% by seed coating with Rhizobium sp. IC 59 and Pseudomonas sp. CDB 35 when compared to captan application. Whereas by seed priming with IC 59 and CDB 35 increased shoot weight by 3
and 39% increase in nodulation was observed. 相似文献