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921.
Symbiobacterium thermophilum is a syntrophic bacterium whose growth depends on coculture with a cognate Bacillus sp. We have been studying the unique features of S. thermophilum in terms of taxonomy, ecology, genome biology, and physiology. Here we overview current knowledge of this bacterium. Although S. thermophilum shows several physiological properties of Gram-negative bacteria, 16S rRNA gene-based phylogeny indicated that it represents a distinct lineage of Gram-positive bacteria with deep branching between the clades for the high-G+C (Actinobacteria) and the low-G+C (Firmicutes) groups. Ecological study has revealed that S. thermophilum and its relatives are widely distributed in the natural environment, including soil, animal intestines and seawater. A whole genome sequencing study uncovered its unusual features, which overall indicate that this bacterium is a member of Firmicutes despite of its high G+C content (68.7%). The genome appeared to retain fully the genes for primary metabolism, except for carbonic anhydrase. We discovered that carbon dioxide is a marked inducer of the mono-growth of S. thermophilum, and speculated that this is due to a lack of carbonic anhydrase. The lines of evidence suggest that S. thermophilum requires additional conditions for full growth, including not only the supply of an unknown positive factor but also the elimination of oxygen and self-growth inhibitory substances. We conclude that the role of the cognate Bacillus is to establish a complex environment suitable for the growth of S. thermophilum, which is achieved by supplying and removing multiple factors. Understandings of this type of mutualism should provide new insight into microbial physiology as well as the issue of uncultivability. 相似文献
922.
Shi JX Li ZX Nitoda T Izumi M Kanzaki H Baba N Kawazu K Nakajima S 《Bioscience, biotechnology, and biochemistry》2007,71(4):1086-1089
Three compounds, 20-O-acetyl-[3-O-(2'E,4'Z)-decadienoyl]-ingenol (1), 20-O-acetyl-[5-O-(2'E,4'Z)-decadienoyl]-ingenol (2) and 3-O-(2'E,4'Z)-decadienoylingenol (3), were isolated from Euphorbia kansui under the bioassay-guided method. Each compound showed the same antinematodal activity against the nematode, Bursaphelenchus xylophilus, at a minimum effective dose (MED) of 5 microg/cotton ball. 相似文献
923.
Tamura S Nitoda T Kubo I 《Zeitschrift für Naturforschung. C, Journal of biosciences》2007,62(3-4):227-233
Salicylic acid slightly inhibited the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) catalyzed by mushroom tyrosinase noncompetitively without being oxidized. In contrast, 4-hydroxybenzoic acid did not inhibit this enzymatic oxidation if a longer reaction time was observed, although it suppressed the initial rate of the oxidation to a certain extent. Neither acid showed noticeable effects on cultured murine B16-F10 melanoma cells except weak cytotoxicity. 相似文献
924.
Cxcl12/Cxcr4 chemokine signaling is required for placode assembly and sensory axon pathfinding in the zebrafish olfactory system 总被引:2,自引:0,他引:2
Positioning neurons in the right places and wiring axons to the appropriate targets are essential events for establishment of neural circuits. In the zebrafish olfactory system, precursors of olfactory sensory neurons (OSNs) assemble into a compact cluster to form the olfactory placode. Subsequently, OSNs differentiate and extend their axons to the presumptive olfactory bulb with high precision. In this study, we aim to elucidate the molecular mechanism underlying these two developmental processes. cxcr4b, encoding a chemokine receptor, is expressed in the migrating olfactory placodal precursors, and cxcl12a (SDF-1a), encoding a ligand for Cxcr4b, is expressed in the abutting anterior neural plate. The expression of cxcr4b persists in the olfactory placode at the initial phase of OSN axon pathfinding. At this time, cxcl12a is expressed along the placode-telencephalon border and at the anterior tip of the telencephalon, prefiguring the route and target of OSN axons, respectively. Interfering with Cxcl12a/Cxcr4b signaling perturbs the assembly of the olfactory placode, resulting in the appearance of ventrally displaced olfactory neurons. Moreover, OSN axons frequently fail to exit the olfactory placode and accumulate near the placode-telencephalon border in the absence of Cxcr4b-mediated signaling. These data indicate that chemokine signaling contributes to both the olfactory placode assembly and the OSN axon pathfinding in zebrafish. 相似文献
925.
926.
Human artificial chromosomes (HACs) are gene-delivery vectors suitable for introducing large DNA fragments into mammalian cells. Although a HAC theoretically incorporates multiple gene expression cassettes of unlimited DNA size, its application has been limited because the conventional gene-loading system accepts only one gene-loading vector (GLV) into a HAC. We report a novel method for the simultaneous or sequential integration of multiple GLVs into a HAC vector (designated as the SIM system) via combined usage of Cre, FLP, Bxb1, and φC31 recombinase/integrase. As a proof of principle, we first attempted simultaneous integration of three GLVs encoding EGFP, Venus, and TdTomato into a gene-loading site of a HAC in CHO cells. These cells successfully expressed all three fluorescent proteins. Furthermore, microcell-mediated transfer of HACs enabled the expression of those fluorescent proteins in recipient cells. We next demonstrated that GLVs could be introduced into a HAC one-by-one via reciprocal usage of recombinase/integrase. Lastly, we introduced a fourth GLV into a HAC after simultaneous integration of three GLVs by FLP-mediated DNA recombination. The SIM system expands the applicability of HAC vectors and is useful for various biomedical studies, including cell reprogramming. 相似文献
927.
Takuya Miyazaki Yong-Soo Kim Jeongheon Yoon Hongsheng Wang Teruhiko Suzuki Herbert C. Morse III 《The Journal of biological chemistry》2014,289(47):32548-32558
The main function of the 3′–5′ DNA exonuclease TREX1 is to digest cytosolic single-stranded DNA to prevent activation of cell-intrinsic responses to immunostimulatory DNA. TREX1 translocates to the nucleus following DNA damage with its nuclear activities being less well defined. Although mutations in human TREX1 have been linked to autoimmune/inflammatory diseases, the mechanisms contributing to the pathogenesis of these diseases remain incompletely understood. Here, using mass spectrometry and co-immunoprecipitation assays and in vivo overexpression models, we show that TREX1 interacts with poly(ADP-ribose) polymerase-1 (PARP1), a nuclear enzyme involved in the DNA damage response. Two zinc finger domains at the amino terminus of PARP1 were required for the interaction with TREX1 that occurs after nuclear translocation of TREX1 in response to DNA damage. Functional studies suggested that TREX1 may contribute to stabilization of PARP1 levels in the DNA damage response and its activity. These results provide new insights into the mechanisms of single-stranded DNA repair following DNA damage and alterations induced by gene mutations. 相似文献
928.
Toru Yoshihara Kazushi Sugihara Yasuhiko Kizuka Shogo Oka Masahide Asano 《The Journal of biological chemistry》2009,284(18):12550-12561
The glycosylation of glycoproteins and glycolipids is important for central
nervous system development and function. Although the roles of several
carbohydrate epitopes in the central nervous system, including polysialic
acid, the human natural killer-1 (HNK-1) carbohydrate, α2,3-sialic acid,
and oligomannosides, have been investigated, those of the glycan backbone
structures, such as Galβ1-4GlcNAc and Galβ1-3GlcNAc, are not fully
examined. Here we report the generation of mice deficient in
β4-galactosyltransferase-II (β4GalT-II). This galactosyltransferase
transfers Gal from UDP-Gal to a nonreducing terminal GlcNAc to synthesize the
Gal β1-4GlcNAc structure, and it is strongly expressed in the central
nervous system. In behavioral tests, the β4GalT-II-/- mice
showed normal spontaneous activity in a novel environment, but impaired
spatial learning/memory and motor coordination/learning. Immunohistochemistry
showed that the amount of HNK-1 carbohydrate was markedly decreased in the
brain of β4GalT-II-/- mice, whereas the expression of
polysialic acid was not affected. Furthermore, mice deficient in
glucuronyltransferase (GlcAT-P), which is responsible for the biosynthesis of
the HNK-1 carbohydrate, also showed impaired spatial learning/memory as
described in our previous report, although their motor coordination/learning
was normal as shown in this study. Histological examination showed abnormal
alignment and reduced number of Purkinje cells in the cerebellum of
β4GalT-II-/- mice. These results suggest that the
Galβ1-4GlcNAc structure in the HNK-1 carbohydrate is mainly synthesized
by β4GalT-II and that the glycans synthesized by β4GalT-II have
essential roles in higher brain functions, including some that are
HNK-1-dependent and some that are not.The glycosylation of glycoproteins, proteoglycans, and glycolipids is
important for their biological activities, stability, transport, and clearance
from circulation, and cell-surface glycans participate in cell-cell and
cell-extracellular matrix interactions. In the central nervous system, several
specific carbohydrate epitopes, including polysialic acid
(PSA),3 the
human natural killer-1 (HNK-1) carbohydrate, α2,3-sialic acid, and
oligomannosides play indispensable roles in neuronal generation, cell
migration, axonal outgrowth, and synaptic plasticity
(1). Functional analyses of the
glycan backbone structures, like lactosamine core (Galβ1-4GlcNAc),
neolactosamine core (Galβ1-3GlcNAc), and polylactosamine
(Galβ1-4GlcNAcβ1-3) have been carried out using gene-deficient mice
in β4-galactosyltransferase-I (β4GalT-I)
(2,
3), β4GalT-V
(4),
β3-N-acetylglucosaminyl-transferase-II (β3GnT-II)
(5), β3GnT-III
(Core1-β3GnT) (6),
β3GnT-V (7), and Core2GnT
(8). However, the roles of
these glycan backbone structures in the nervous system have not been examined
except the olfactory sensory system
(9).β4GalTs synthesize the Galβ1-4GlcNAc structure via the
β4-galactosylation of glycoproteins and glycolipids; the β4GalTs
transfer galactose (Gal) from UDP-Gal to a nonreducing terminal
N-acetylglucosamine (GlcNAc) of N- and O-glycans
with a β-1,4-linkage. The β4GalT family has seven members
(β4GalT-I to VII), of which at least five have similar
Galβ1-4GlcNAc-synthesizing activities
(10,
11). Each β4GalT has a
tissue-specific expression pattern and substrate specificity with overlapping,
suggesting each β4GalT has its own biological role as well as redundant
functions. β4GalT-I and β4GalT-II share the highest identity (52% at
the amino acid level) among the β4GalTs
(12), suggesting these two
galactosyltransferases can compensate for each other. β4GalT-I is
strongly and ubiquitously expressed in various non-neural tissues, whereas
β4GalT-II is strongly expressed in neural tissues
(13,
14). Indeed, the β4GalT
activity in the brain of β4GalT-I-deficient (β4GalT-I-/-)
mice remains as high as 65% of that of wild-type mice, and the expression
levels of PSA and the HNK-1 carbohydrate in the brain of these mice are normal
(15). These results suggest
β4GalTs other than β4GalT-I, like β4GalT-II, are important in
the nervous system.Among the β4GalT family members, only β4GalT-I-/- mice
have been examined extensively; this was done by us and another group. We
reported that glycans synthesized by β4GalT-I play various roles in
epithelial cell growth and differentiation, inflammatory responses, skin wound
healing, and IgA nephropathy development
(2,
16-18).
Another group reported that glycans synthesized by β4GalT-I are involved
in anterior pituitary hormone function and in fertilization
(3,
19). However, no other nervous
system deficits have been reported in these mice, and the role of the
β4-galactosylation of glycoproteins and glycolipids in the nervous system
has not been fully examined.In this study, we generated β4GalT-II-/- mice and examined
them for behavioral abnormalities and biochemical and histological changes in
the central nervous system. β4GalT-II-/- mice were impaired in
spatial learning/memory and motor coordination/learning. The amount of HNK-1
carbohydrate was markedly decreased in the β4GalT-II-/- brain,
but PSA expression was not affected. These results suggest that the
Galβ1-4GlcNAc structure in the HNK-1 carbohydrate is mainly synthesized
by β4GalT-II and that glycans synthesized by β4GalT-II have
essential roles in higher brain functions, including ones that are HNK-1
carbohydrate-dependent and ones that are independent of HNK-1. 相似文献
929.
Kazuko Tsuchihara Tetsuichi Wazawa Toshio Yanagida Xiang-Guo Zheng Kazuo Yoshihara Fumio Tokunaga 《FEBS letters》2009,583(2):345-349
A native female-specific chemoreceptive protein of a swallowtail butterfly [oviposition stimulant binding protein (OSBP)] was shown to specifically bind to aristolochic acid, a main stimulant for oviposition from its host plant. Oviposition stimulants are recognized by chemoreceptive organs of insects. OSBP isolated previously from the chemoreceptive organs was assumed to bind to an oviposition stimulant. Using a highly sensitive fluorescent micro-binding assay, we clarified OSBP bound to aristolochic acid. Three-dimensional molecular modeling revealed the structure of the OSBP-aristolochic acid complex. This is the first report of a native chemoreceptive protein binding to an oviposition stimulant as a ligand in insects. 相似文献
930.
The phenomenon of the developmental arrest at the 2-cell stage of 1-cell embryos from some mouse strains during in vitro culture is known as the 2-cell block. We investigated the specific factors involved in the 2-cell block of AKR embryos by means of a modified culture system, the production of reconstructed embryos by pronuclear exchange and a cross experiment. In a culture medium with phosphate, 94.6% of 1-cell embryos from the C57BL mouse strain developed to the blastocyst stage, but 95.7% of embryos from the AKR mouse strain showed 2-cell block. Phosphate-free culture medium rescued the 2-cell block of AKR embryos and accelerated the first cell cycle of the embryos. Co-culture with BRL cells and a BRL-conditioned medium fractionated below 30 kDa also rescued the 2-cell block of AKR embryos. Examinations of in vitro development of reconstructed embryos and of embryos from F1 females between AKR and C57BL strains clearly demonstrated that the AKR cytoplast caused the 2-cell block. In the backcrossed female progeny between (AKR x C57BL) F1 males and AKR females, about three-quarters of the embryos were of the 2-cell blocking phenotype and about one-quarter were of the non-blocking phenotype. These results suggest that two genes are responsible for the 2-cell block of AKR embryos. 相似文献