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1.
Gloria Salazar Stephanie Zlatic Branch Craige Andrew A. Peden Jan Pohl Victor Faundez 《The Journal of biological chemistry》2009,284(3):1790-1802
The Hermansky-Pudlak syndrome is a disorder affecting endosome sorting.
Disease is triggered by defects in any of 15 mouse gene products, which are
part of five distinct cytosolic molecular complexes: AP-3, homotypic fusion
and vacuole protein sorting, and BLOC-1, -2, and -3. To identify molecular
associations of these complexes, we used in vivo cross-linking
followed by purification of cross-linked AP-3 complexes and mass spectrometric
identification of associated proteins. AP-3 was co-isolated with BLOC-1,
BLOC-2, and homotypic fusion and vacuole protein sorting complex subunits;
clathrin; and phosphatidylinositol-4-kinase type II α (PI4KIIα).
We previously reported that this membrane-anchored enzyme is a regulator of
AP-3 recruitment to membranes and a cargo of AP-3 (Craige, B.,
Salazar, G., and Faundez, V. (2008) Mol. Biol.
Cell
19,1415
-1426). Using cells deficient
in different Hermansky-Pudlak syndrome complexes, we identified that BLOC-1,
but not BLOC-2 or BLOC-3, deficiencies affect PI4KIIα inclusion into
AP-3 complexes. BLOC-1, PI4KIIα, and AP-3 belong to a tripartite
complex, and down-regulation of either PI4KIIα, BLOC-1, or AP-3
complexes led to similar LAMP1 phenotypes. Our analysis indicates that BLOC-1
complex modulates the association of PI4KIIα with AP-3. These results
suggest that AP-3 and BLOC-1 act, either in concert or sequentially, to
specify sorting of PI4KIIα along the endocytic route.Membranous organelles along the exocytic and endocytic pathways are each
defined by unique lipid and protein composition. Vesicle carriers communicate
and maintain the composition of these organelles
(2). Consequently defining the
machineries that specify vesicle formation, composition, and delivery are
central to understanding membrane protein traffic. Generally vesicle
biogenesis uses multiprotein cytosolic machineries to select membrane
components for inclusion in nascent vesicles
(2,
3). Heterotetrameric adaptor
complexes (AP-1 to AP-4) are critical to generate vesicles of specific
composition from the different organelles constituting the exocytic and
endocytic routes
(2-4).The best understood vesicle formation machinery in mammalian cells is the
one organized around the adaptor complex AP-2
(5). This complex generates
vesicles from the plasma membrane using clathrin. Our present detailed
understanding of AP-2 vesicle biogenesis mechanisms and interactions emerged
from a combination of organellar and in vitro binding proteomics
analyses together with the study of binary interactions in cell-free systems
(5-9).
In contrast, the vesicle biogenesis pathways controlled by AP-3 are far less
understood. AP-3 functions to produce vesicles that traffic selected membrane
proteins from endosomes to lysosomes, lysosome-related organelles, or synaptic
vesicles
(10-13).
AP-3 is one of the protein complexes affected in the Hermansky-Pudlak syndrome
(HPS;3 Online
Mendelian Inheritance in Man (OMIM) 203300). So far, mutations in any of 15
mouse or eight human genes trigger a common syndrome. This syndrome
encompasses defects that include pigment dilution, platelet dysfunction,
pulmonary fibrosis, and occasionally neurological phenotypes
(14,
15). All forms of HPS show
defective vesicular biogenesis or trafficking that affects lysosomes,
lysosome-related organelles (for example melanosomes and platelet dense
granules), and, in some of them, synaptic vesicles
(11-13).
Most of the 15 HPS loci encode polypeptides that assemble into five distinct
molecular complexes: the adaptor complex AP-3, HOPS, and the BLOC complexes 1,
2, and 3 (14). Recently binary
interactions between AP-3 and BLOC-1 or BLOC-1 and BLOC-2 suggested that
arrangements of these complexes could regulate membrane protein targeting
(16). Despite the abundance of
genetic deficiencies leading to HPS and genetic evidence that HPS complexes
may act on the same pathway in defined cell types
(17), we have only a partial
picture of protein interactions organizing these complexes and how they might
control membrane protein targeting.In this study, we took advantage of cell-permeant and reversible
cross-linking of HPS complexes followed by their immunoaffinity purification
to identify novel molecular interactions. Cross-linked AP-3 co-purified with
BLOC-1, BLOC-2, HOPS, clathrin, and the membrane protein PI4KIIα. We
previously identified PI4KIIα as a cargo and regulator of AP-3
recruitment to endosomes (1,
18). Using mutant cells
deficient in either individual HPS complexes or a combination of them, we
found that BLOC-1 facilitates the interaction of AP-3 and PI4KIIα. Our
studies demonstrate that subunits of four of the five HPS complexes co-isolate
with AP-3. Moreover BLOC-1, PI4KIIα, and AP-3 form a tripartite complex
as demonstrated by sequential co-immunoprecipitations as well as by similar
LAMP1 distribution phenotypes induced by down-regulation of components of this
tripartite complex. Our findings indicate that BLOC-1 complex modulates the
recognition of PI4KIIα by AP-3. These data suggest that AP-3, either in
concert or sequentially with BLOC-1, participates in the sorting of common
membrane proteins along the endocytic route. 相似文献
2.
Cell death can be divided into the anti-inflammatory process of apoptosis and the
pro-inflammatory process of necrosis. Necrosis, as apoptosis, is a regulated form of cell
death, and Poly-(ADP-Ribose) Polymerase-1 (PARP-1) and Receptor-Interacting Protein (RIP)
1/3 are major mediators. We previously showed that absence or inhibition of PARP-1
protects mice from nephritis, however only the male mice. We therefore hypothesized that
there is an inherent difference in the cell death program between the sexes. We show here
that in an immune-mediated nephritis model, female mice show increased apoptosis compared
to male mice. Treatment of the male mice with estrogens induced apoptosis to levels
similar to that in female mice and inhibited necrosis. Although PARP-1 was activated in
both male and female mice, PARP-1 inhibition reduced necrosis only in the male mice. We
also show that deletion of RIP-3 did not have a sex bias. We demonstrate here that male
and female mice are prone to different types of cell death. Our data also suggest that
estrogens and PARP-1 are two of the mediators of the sex-bias in cell death. We therefore
propose that targeting cell death based on sex will lead to tailored and better treatments
for each gender. 相似文献
3.
4.
Omar A. Ramírez René L. Vidal Judith A. Tello Karina J. Vargas Stefan Kindler Steffen H?rtel Andrés Couve 《The Journal of biological chemistry》2009,284(19):13077-13085
Understanding the mechanisms that control synaptic efficacy through the
availability of neurotransmitter receptors depends on uncovering their
specific intracellular trafficking routes. γ-Aminobutyric acid type B
(GABAB) receptors (GABABRs) are obligatory heteromers
present at dendritic excitatory and inhibitory postsynaptic sites. It is
unknown whether synthesis and assembly of GABABRs occur in the
somatic endoplasmic reticulum (ER) followed by vesicular transport to
dendrites or whether somatic synthesis is followed by independent transport of
the subunits for assembly and ER export throughout the somatodendritic
compartment. To discriminate between these possibilities we studied the
association of GABABR subunits in dendrites of hippocampal neurons
combining live fluorescence microscopy, biochemistry, quantitative
colocalization, and bimolecular fluorescent complementation. We demonstrate
that GABABR subunits are segregated and differentially mobile in
dendritic intracellular compartments and that a high proportion of
non-associated intracellular subunits exist in the brain. Assembled heteromers
are preferentially located at the plasma membrane, but blockade of ER exit
results in their intracellular accumulation in the cell body and dendrites. We
propose that GABABR subunits assemble in the ER and are exported
from the ER throughout the neuron prior to insertion at the plasma membrane.
Our results are consistent with a bulk flow of segregated subunits through the
ER and rule out a post-Golgi vesicular transport of preassembled
GABABRs.The efficacy of synaptic transmission depends on the intracellular
trafficking of neurotransmitter receptors
(1,
2). The trafficking of
glutamatergic and
GABAA6
receptors has been extensively studied, and their implications for synaptic
plasticity have been well documented
(3,
4). For example, differential
trafficking of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid
(AMPA) receptors modifies synaptic strength and influences
experience-dependent plasticity in vivo
(5). The molecular mechanisms
that govern the trafficking of metabotropic GABABRs and their
consequences for synaptic inhibition remain less clear. In particular, limited
information is available regarding the relationship between the trafficking of
GABABRs and the topological complexity of the secretory pathway in
neurons.GABABRs mediate the slow component of synaptic inhibition by
acting on pre- and postsynaptic targets
(6–8).
They are implicated in epilepsy, anxiety, stress, sleep disorders,
nociception, depression, and cognition
(9). They also represent
attractive targets for the treatment of withdrawal symptoms from drugs of
addiction such as cocaine
(10). They are obligatory
heteromers composed of GABABR1 and GABABR2 subunits.
GABABR1 contains an RXR-type sequence in the intracellular
C-terminal domain that functions as an ER retention motif
(11,
12). The ER retention sequence
is masked upon assembly with GABABR2 resulting in the appearance of
functional receptors at the plasma membrane. Only GABABR1 binds
GABA with high affinity, whereas G protein signaling is exclusively mediated
by the second and third intracellular loops of GABABR2
(13–15).
GABABRs are located in dendrites and axons, but their distribution
does not coincide with the active zone or the postsynaptic density. Rather,
they are adjacent to both compartments constituting perisynaptic receptors
(16,
17).If GABABR subunits are synthesized in the soma, at least two
possibilities exist for their anterograde transport, assembly, and insertion
in dendrites. First, the subunits may be synthesized in the cell body,
assembled in the somatic ER, and targeted preassembled in post-Golgi vesicles
to their site of insertion in dendrites. Alternatively, they may be
synthesized in the soma and transported through the ER membrane as
non-heteromeric subunits. In the latter scenario, newly assembled receptors
may exit the ER throughout the somatodendritic compartment prior to insertion
at the plasma membrane and diffuse laterally for retention at functional
sites. No evidence exists to discriminate between these possibilities. We
reasoned that a prevalence of associated subunits in post-Golgi vesicles in
dendrites would favor the first alternative, whereas the existence of
non-associated subunits in intracellular compartments would support a
somatodendritic assembly mechanism. Here we explore the presence of associated
GABABR subunits using fluorescence recovery after photobleaching
(FRAP), biochemistry, and quantitative colocalization. In addition, we report
for the first time the use of BiFC
(18) to study
GABABR assembly in neurons. Our results demonstrate that
GABABR subunits are differentially mobile in dendrites and that a
high proportion of non-associated subunits prevail in an intracellular
fraction of the adult brain. They also show that GABABR subunits
are heteromeric at the plasma membrane but segregated in intracellular
compartments of dendrites of hippocampal neurons. Importantly, treatment with
brefeldin A (BFA) or interference of the coatomer protein complex II impair ER
export and result in the accumulation of assembled subunits in intracellular
compartments throughout the somatodendritic arbor. We conclude that
GABABR subunits are synthesized in the soma and remain segregated
in intracellular compartments prior to somatodendritic assembly. Our
observations rule out a post-Golgi vesicular transport of preassembled
GABABRs and suggest an alternative mechanism of receptor
targeting. 相似文献
5.
Background
The presence of β-lactamases in Y. enterocolitica has been reported to vary with serovars, biovars and geographical origin of the isolates. An understanding of the β-lactamases in other related species is important for an overall perception of antibiotic resistance in yersiniae. The objective of this work was to study the characteristics of β-lactamases and their genes in strains of Y. intermedia and Y. frederiksenii, isolated from clinical and non-clinical sources in India. 相似文献6.
Guo-Dong Li David C. Chiara Jonathan B. Cohen Richard W. Olsen 《The Journal of biological chemistry》2009,284(18):11771-11775
Photoaffinity labeling of γ-aminobutyric acid type A
(GABAA)-receptors (GABAAR) with an etomidate analog and
mutational analyses of direct activation of GABAAR by neurosteroids
have each led to the proposal that these structurally distinct general
anesthetics bind to sites in GABAARs in the transmembrane domain at
the interface between the β and α subunits. We tested whether the
two ligand binding sites might overlap by examining whether neuroactive
steroids inhibited etomidate analog photolabeling. We previously identified
(Li, G. D., Chiara, D. C., Sawyer, G. W., Husain, S. S., Olsen, R. W., and
Cohen, J. B. (2006) J. Neurosci. 26, 11599–11605) azietomidate
photolabeling of GABAAR α1Met-236 and βMet-286 (in
αM1 and βM3). Positioning these two photolabeled amino acids in a
single type of binding site at the interface of β and α subunits
(two copies per pentamer) is consistent with a GABAAR homology
model based upon the structure of the nicotinic acetylcholine receptor and
with recent αM1 to βM3 cross-linking data. Biologically active
neurosteroids enhance rather than inhibit azietomidate photolabeling, as
assayed at the level of GABAAR subunits on analytical SDS-PAGE, and
protein microsequencing establishes that the GABAAR-modulating
neurosteroids do not inhibit photolabeling of GABAAR
α1Met-236 or βMet-286 but enhance labeling of α1Met-236. Thus
modulatory steroids do not bind at the same site as etomidate, and neither of
the amino acids identified as neurosteroid activation determinants (Hosie, A.
M., Wilkins, M. E., da Silva, H. M., and Smart, T. G. (2006) Nature
444, 486–489) are located at the subunit interface defined by our
etomidate site model.GABAA3
receptors (GABAAR) are major mediators of brain inhibitory
neurotransmission and participate in most circuits and behavioral pathways
relevant to normal and pathological function
(1). GABAAR are
subject to modulation by endogenous neurosteroids, as well as myriad
clinically important central nervous system drugs including general
anesthetics, benzodiazepines, and possibly ethanol
(1,
2). The mechanism of
GABAAR modulation by these different classes of drugs is of major
interest, including identification of the receptor amino acid residues
involved in binding and action of the drugs.In the absence of high resolution crystal structures of drug-receptor
complexes, the locations of anesthetic binding sites in GABAARs
have been predicted based upon analyses of functional properties of point
mutant receptors, which identified residues in the α and β subunit
M1–M4 transmembrane helices important for modulation by volatile
anesthetics (primarily α subunit) and by intravenous agents, including
etomidate and propofol (β subunit)
(3–5).
Position βM2–15, numbered relative to the N terminus of the helix,
functions as a major determinant of etomidate and propofol potency as GABA
modulators in vitro and in vivo
(6–8).
By contrast, this residue is not implicated for modulation by the
neurosteroids, potent endogenous modulators of GABAAR
(9).Photoaffinity labeling, which allows the identification of residues in
proximity to drug binding sites
(10,
11), has been used to identify
two GABAAR amino acids covalently modified by the etomidate analog
[3H]azietomidate
(12): α1Met-236 within
αM1 and βMet-286 within βM3. Photolabeling of these residues
was inhibited equally by nonradioactive etomidate and enhanced proportionately
by GABA present in the assay, consistent with the presence of these two
residues in a common drug binding pocket that would be located at the
interface between the β and α subunits in the transmembrane domain
(12). Mutational analyses
identify these positions as etomidate and propofol sensitivity determinants
(13–15).A recent mutagenesis study
(16) identified two other
residues in GABAAR αM1 and βM3 as critical for direct
activation by neurosteroids, αThr-236 (rat numbering, corresponding to
α1Thr-237, bovine numbering used here and by Li et al.
(12))4
and βTyr-284. These residues were also proposed to contribute to a
neurosteroid binding pocket in the transmembrane domain at the interface
between β and α subunits, based upon their location in an
alternative GABAAR structural model that positioned those amino
acids, and not α1Met-236 or βMet-286, at the subunit interface. For
GABAARs and other members of the Cys-loop superfamily of
neurotransmitter-gated ion channels, the transmembrane domain of each subunit
is made up of a loose bundle of four α helices (M1–M4), with M2
from each subunit contributing to the lumen of the ion channel and M4
positioned peripherally in greatest contact with lipid, as seen in the
structures of the Torpedo nicotinic acetylcholine receptor (nAChR)
(17) and in distantly related
prokaryote homologs (18).
However, uncertainties in the alignment of GABAAR subunit sequences
relative to those of the nAChR result in alternative GABAAR
homology models (12,
19,
20) that differ in the
location of amino acids in the M3 and M4 membrane-spanning helices and in the
M1 helix in some models (16,
21).If etomidate and neurosteroids both bind at the same β/α
interface in the GABAAR transmembrane domain, the limited space
available for ligand binding suggests that their binding pockets might overlap
and that ligand binding would be mutually exclusive. To address this question,
we photolabeled purified bovine brain GABAAR with
[3H]azietomidate in the presence of different neuroactive steroids
and determined by protein microsequencing whether active neurosteroids
inhibited labeling of α1Met-236 and βMet-286, as expected for
mutually exclusive binding, or resulted in [3H]azietomidate
photolabeling of other amino acids, a possible consequence of allosteric
interactions. Active steroids failed to inhibit labeling and enhanced labeling
of α1Met-236, clearly indicating that the neurosteroid and the etomidate
sites are distinct. Our GABAAR homology model that positions
α1Met-236 and βMet-286 at the β/α interface, but not
that of Hosie et al.
(16), is also consistent with
cysteine substitution cross-linking studies
(20,
22), which define the
proximity relations between amino acids in the αM1, αM2,
αM3, and βM3 helices, and these results support the interpretation
that the two residues photolabeled by [3H]azietomidate are part of
a single subunit interface binding pocket, whereas the steroid sensitivity
determinants identified by mutagenesis neither are at the β/α
subunit interface nor are contributors to a common binding pocket. 相似文献
7.
8.
I. Yu. Volkov N. A. Lunina O. V. Berezina G. A. Velikodvorskaya V. V. Zverlov 《Molecular Biology》2005,39(6):799-805
9.
M. Zapater M. Catterou B. Mary M. Ollier L. Fingar E. Mignot F. Ferchaud L. Strullu F. Dubois M. Brancourt-Hulmel 《Bioenergy Research》2017,10(1):115-128
The sustainable development of miscanthus as a bioenergy feedstock requires optimizing its fertilizer inputs and, therefore, determining its nitrogen (N) requirements. The ‘critical nitrogen dilution curve’ is a powerful tool to characterize such N requirements; it relates the N concentration ([N]) in aboveground organs to their biomass, defining two domains depending on whether the N factor limits biomass growth or not. We aimed to develop such a tool in miscanthus. Using a rhizome N depletion strategy with green cutting pre-treatment over several years before the start of the experiment, we grew, in 2014, two cultivated species, Miscanthus × giganteus (M×g) and Miscanthus sinensis (Msin), at four fertilizer levels (0, 80, 160 and 240 kg N ha?1). We found a strong nitrogen fertilization effect. The shoot [N] decreased as the aboveground biomass increased in both species and in all of the treatments. [N] was strongly correlated with leaf/stem biomass ratio. The N treatments enabled the identification of the observed critical points, i.e. points with the maximum biomass (W) and the lowest [N], on each measurement date. These points could be fitted to the following critical dilution curve that was common between M×g and Msin: N concentration (Nc) (critical [N], g N kg?1) = 27.0 W ?0.48 when W > 1 t ha?1 and Nc = 27.0 when W ≤ 1. This curve was validated by literature data, separated into N-limited or not-limited conditions. The similarity of the curves between the two species was due to compensation between leaf/stem biomass ratio and [N] in the stems. This curve is helpful to diagnose the crop N status and define the optimal fertilizer requirements of miscanthus crops. 相似文献
10.
11.
Much attention has been focused on the study of lactoferrin at the protein or nucleotide level in mice, humans, and cattle, but little is known about it in goats. The goat LF gene from 5' UTR to exon 17 was amplified, and the variation of g.7605C→T in 10 Chinese indigenous goat breeds was analyzed. Among the three ruminant species (cattle, sheep, and goats), the intron-exon distribution pattern was similar, and all the exons had the same length, but the length of introns varied greatly due to insertions or deletions. The frequency of allele T at g.7605C→T (50.12%) was a little higher than that of allele C (49.88%), and the genotype distribution differed greatly between goat populations. The g.7605C→T site showed higher genetic diversity in goat populations. The genetic differentiation was 0.0783, and gene flow was 2.9433 among the 10 Chinese indigenous goat populations. 相似文献
12.
Shimonaga T Fujiwara S Kaneko M Izumo A Nihei S Francisco PB Satoh A Fujita N Nakamura Y Tsuzuki M 《Marine biotechnology (New York, N.Y.)》2007,9(2):192-202
Red algae are widely known to produce floridean starch but it remains unclear whether the molecular structure of this algal polyglucan is distinct from that of the starch synthesized by vascular plants and green algae. The present study shows that the unicellular species Porphyridium purpureum R-1 (order Porphyridiales, class Bangiophyceae) produces both amylopectin-type and amylose-type alpha-polyglucans. In contrast, Cyanidium caldarium (order Porphyridiales, class Bangiophyceae) synthesizes glycogen-type polyglucan, but not amylose. Detailed analysis of alpha-1,4-chain length distribution of P. purpureum polyglucan suggests that the branched polyglucan has a less ordered structure, referred to as semi-amylopectin, as compared with amylopectin of rice endosperm having a tandem-cluster structure. The P. purpureum linear amylose-type polyglucan, which has a lambda(max) of 630 nm typical of amylose-iodine complex and is resistant to Pseudomonas isoamylase digestion, accounts for less than 10% of the total polyglucans. We produced and isolated a cDNA encoding a granule-bound starch synthase (GBSS)-type protein of P. purpureum, which is probably the approximately 60-kDa protein bound tightly to the starch granules, resembling the amylose-synthesizing GBSS protein of green plants. The present investigation indicates that the class Bangiophyceae includes species producing both semi-amylopectin and amylose, and species producing glycogen alone. 相似文献
13.
A. E. Zemlyakov V. N. Tsikalova V. V. Tsikalov V. Ya. Chirva E. L. Mulik F. N. Kuzovlev O. V. Kalyuzhin M. V. Kiselevsky 《Russian Journal of Bioorganic Chemistry》2008,34(1):103-109
Symmetric secondary linear alcohols were proposed as aglycones for the synthesis of lipophilic glycosides of β-N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP). Pentadecan-8-ol, nonadecan-10-ol, and tricosan-12-ol were glycosylated by the oxazoline method. Based on the corresponding glucosaminides, alkyl β-glycosides of 4,6-O-isopropylidene-N-acetylmuramic acid were synthesized and coupled with the dipeptide. Deprotection of isopropylidene groups by acidic hydrolysis and catalytic hydrogenolysis of benzyl esters resulted in the target muramyldipeptide glycosides. Nonadecan-10-yl and tricosan-12-yl β-MDPs at doses 2 μg/mice most effectively stimulated antibacterial resistance in mice against Staphylococcus aureus. In contrast to the previously synthesized undecan-6-yl β-MDP, pentadecan-8-yl, nonadecan-10-yl, and tricosan-12-yl β-MDPs demonstrated direct cytotoxicity toward tumor cells K-562 and blood mononuclear cells. 相似文献
14.
15.
D. N. Karimova I. V. Manukhov E. Yu. Gnuchikh I. F. Karimov D. G. Deryabin 《Applied Biochemistry and Microbiology》2016,52(3):269-276
The effect of reactive oxygen and nitrogen species on lux-biosensors based on the Escherichia coli K12 MG1655 and Salmonella typhimurium LT2 host strains was investigated. The bioactivity of exogenous free radicals to the constitutively luminescent E. coli strain with plasmid pXen7 decreased in the order H2O2 > OCl– > NO? > RОO? > ONOO–> O2?- while the bioluminescence of S. typhimurium strain transformed with this plasmid decreased in the order NO? > H2O2 > ONOO– > RОO? > OCl– > O2?- The cross-reactivity of induced lux-biosensors to reactive oxygen and nitrogen species, the threshold sensitivity and the luminescence amplitude dependences from the plasmid specificity and the host strain were indicated. The biosensors with plasmid pSoxS′::lux possessed a wider range of sensitivity, including H2O2 and OCl–, along with O2?- and NO?. Among the used reactive oxygen and nitrogen species, H2O2 showed the highest induction activity concerning to the plasmids pKatG′::lux, pSoxS′::lux and pRecA′::lux. The inducible lux-biosensors based on S. typhimurium host strain possessed a higher sensitivity to the reactive oxygen and nitrogen species in comparison with the E. coli lux-biosensors. 相似文献
16.
The following glycosides of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) were synthesized: β-4-tert-butylcyclohexyl MDP, β-2-(adamant-1-yl)ethyl MDP, β-2,2-diphenylethyl MDP, and β-2-(p-biphenyl) ethyl MDP. The starting peracetylated β-N-acetylglucosaminides were prepared by the oxazoline method. They were converted into 4,6-O-isopropylidene-N-acetyl-D-muramic acids, which were coupled with L-Ala-D-Glu(NH2)OBn. The target glycopeptides were obtained after their deprotection. The stimulation of the anti-infection resistance of mice against Staphylococcus aureus by the MDP glycosides was studied. 相似文献
17.
M. V. Semenova M. I. Drachevskaya O. A. Sinitsyna A. V. Gusakov A. P. Sinitsyn 《Biochemistry. Biokhimii?a》2009,74(9):1002-1008
Homogeneous β-xylosidases with molecular mass values 120 and 80 kDa (as shown by SDS-PAGE), belonging to the third family
of glycosyl hydrolases, were isolated by anion-exchange, hydrophobic, and gel-penetrating chromatography from enzyme preparations
based on the fungi Aspergillus japonicus and Trichoderma reesei, respectively. The enzymes exhibit maximal activity in acidic media (pH 3.5–4.0), and temperature activity optimum was 70°C
for the β-xylosidase of A. japonicus and 60°C for the β-xylosidase of T. reesei. Kinetic parameters of p-nitrophenyl β-xylopyranoside and xylooligosaccharide hydrolysis by the purified enzymes were determined, which showed that
β-xylosidase of A. japonicus was more specific towards low molecular weight substrates, while β-xylosidase of T. reesei preferred high molecular weight substrates. The competitive type of inhibition by reaction product (xylose) was found for
both enzymes. The interaction of the enzymes of different specificity upon hydrolysis of glucurono- and arabinoxylans was
found. The β-xylosidases exhibit synergism with endoxylanase upon hydrolysis of glucuronoxylan as well as with α-L-arabinofuranosidase
and endoxylanase upon hydrolysis of arabinoxylan. Addition of β-xylosidases increased efficiency of hydrolysis of plant raw
materials with high hemicellulose content (maize cobs) by the enzymic preparation Celloviridine G20x depleted of its own β-xylosidase. 相似文献
18.
Rejane Flores Daniela BrondaniJr Verciane CezarottoJr Sandro Rogério Giacomelli Fernando Teixeira Nicoloso 《In vitro cellular & developmental biology. Plant》2010,46(2):210-217
The aim of this study was to investigate both a mass in vitro propagation system and the β-ecdysone content in roots and aerial parts of Pfaffia glomerata and Pfaffia tuberosa. Nodal segments of two genotypes (BRA and JB-UFSM) of P. glomerata, originated from aseptically grown plants, were cultivated on hormone-free Murashige and Skoog medium. For the proliferation
of P. tuberosa shoots, nodal segments, originated from aseptically grown plants, were either cultivated on hormone-free Murashige and Skoog
(MS) medium or were supplemented with 1.0 μM thidiazuron (TDZ); the elongation and rooting of these plants were carried out
on MS medium without TDZ. Plantlets of both species were acclimatized and transferred to field conditions. The β-ecdysone
content in the plants was determined by high performance liquid chromatography. The BRA genotype showed a greater in vitro proliferation rate and β-ecdysone content than that of the JB-UFSM genotype. The culture of nodal segments of P. tuberosa on medium with 1.0 μM TDZ with subsequent subcultivation of shoots on hormone-free medium was shown to be a suitable method
for micropropagation due to the high multiplication rate and good plant development. Both species showed good adaptation to
ex vitro conditions. The β-ecdysone content in micropropagated P. tuberosa was similar to that found in field-grown plants. For both species, the aerial parts accumulated higher β-ecdysone content
than roots. These results reveal that micropropagation is a successful, alternative method for rapid plant multiplication
of both species of Brazilian ginseng. Furthermore, this study demonstrates that these two species have a potential for cultivation
that is associated with high β-ecdysone production. 相似文献
19.
20.
C. violaceum appeared as important bacterium in different applications and mainly these aspects are related to the production of violacein.
This review discusses the last reports on biosynthetic pathways, production, genetic aspects, biological activities, pathological
effects, antipathogenic screening through quorum sensing, environmental effects and the products of C. violaceum with industrial interest. An important discussion is on biological applications in medicine and as industrial products such
as textile and in cosmetics. 相似文献