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951.
Masato Maruyama Naomi Arisaka Yoshikuni Goto Yosuke Ohsawa Hideshi Inoue Hiroshi Fujiwara Akira Hattori Masafumi Tsujimoto 《The Journal of biological chemistry》2009,284(50):34692-34702
Human laeverin/aminopeptidase Q (LVRN/APQ) is a novel member of the M1 family of zinc aminopeptidases and is specifically expressed on the cell surface of human extravillous trophoblasts. Multiple sequence alignment of human M1 aminopeptidase revealed that the first Gly residue within the conserved exopeptidase motif of the M1 family, GXMEN motif, is uniquely substituted for His in human LVRN/APQ. In this study, we evaluated the roles of nonconserved His379, comprising the exopeptidase motif in the enzymatic properties of human LVRN/APQ. We revealed that the substitution of His379 with Gly caused significant changes in substrate specificity both toward fluorogenic substrates and natural peptide hormones. In addition, the susceptibilities of bestatin, a sensitive inhibitor for human LVRN/APQ, and natural inhibitory peptides were decreased in the H379G mutant. A molecular model suggested a conformational difference between wild-type and H379G human LVRN/APQs. These results indicate that His379 of the enzyme plays essential roles in its distinctive enzymatic properties and contributes to maintaining the appropriate structure of the catalytic cavity of the enzyme. Our data may bring new insight into the biological significance of the unique exopeptidase motif of LVRN/APQ obtained during the evolution of primates. 相似文献
952.
Ken Horii Takashi Adachi Tetsuya Matsuda Tsutomu Tanaka Hiroshi Sahara Seiji Shibasaki Chiaki Ogino Yoji Hata Mitsuyoshi Ueda Akihiko Kondo 《Journal of Molecular Catalysis .B, Enzymatic》2009,59(4):297-301
β-Glucosidase (BGL1) from Aspergillus oryzae was efficiently produced in recombinant A. oryzae using sodM promoter-mediated expression system. The yield of BGL1 was 960 mg/l in liquid culture, which is 20-fold higher than the yield of BGL1 produced using the yeast Saccharomyces cerevisiae. Recombinant BGL1 converted isoflavone glycosides into isoflavone aglycones more efficiently than β-glucosidase from almond. In addition, BGL1 produced isoflavone aglycones even in the presence of the insoluble form of isoflavone glycosides. 相似文献
953.
Vyjayanthi F. Lopez Moses T. K. Kairo Gene V. Pollard Charles Pierre Naomi Commodore Donny Dominique 《BioControl》2009,54(4):497-503
Four years after the release of two exotic parasitoids, Amitus hesperidum Silvestri (Hymenoptera: Platygasteridae) and Encarsia perplexa Huang and Polaszek (Hymenoptera: Aphelinidae) for the classical biological control of the citrus blackfly (CBF), Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) in Dominica, a survey was conducted to assess establishment as well as potential nontarget
effects especially on Aleyrodidae and other related taxa. CBF populations were low to non-existent in 50 of 51 field sites
examined. At the site where CBF was encountered, both E. perplexa and A. hesperidum were present and CBF populations were declining. The two parasitoids were not among the several species collected on nontarget
Aleryodidae and Hemiptera. It is concluded that E. perplexa and A. hesperidum have kept CBF populations under effective biological control in Dominica and there is no evidence of any nontarget effects
on other Aleyrodidae or their natural enemies.
Handling Editor: Dirk Babendreier. 相似文献
954.
Characterization of the intestinal microbiota of two Antarctic notothenioid fish species 总被引:2,自引:0,他引:2
Naomi L. Ward Blaire Steven Kevin Penn Barbara A. Methé William H. Detrich III 《Extremophiles : life under extreme conditions》2009,13(4):679-685
The fish fauna of the Southern Ocean is dominated by species of the perciform suborder Notothenioidei, which constitute 46%
of fish species and 90% of biomass. Notothenioids have undergone rapid morphological and ecological diversification and developed
physiological adaptations to a cold, highly oxygenated environment. Microbes inhabiting animal intestines include those that
perform essential nutritional functions, but notothenioid gut microbial communities have not been investigated using cultivation-independent
approaches. We analyzed bacterial 16S rRNA gene sequences obtained from the intestinal tract of Notothenia coriiceps and Chaenocephalus aceratus, which differ in their pelagic distribution and feeding strategies. Both samples showed dominance of Gammaproteobacteria
(mostly Vibrionaceae), as has been reported for temperate teleost species. Both samples showed low diversity relative to that reported for other
fish microbiota studies, with C. aceratus containing fewer OTUs than N. coriiceps. Despite the small sample size of this preliminary study, our findings suggest that Antarctic notothenioids carry a gut microbiota
similar in composition to that of temperate fish, but exhibiting lower species-level diversity. The omnivorous N. coriiceps individual exhibited greater diversity than the exclusively carnivorous C. aceratus individual, which may indicate that increasing herbivory in fish leads to gut microbe diversification, as found in mammals.
Lastly, we detected members of taxa containing known microbial pathogens, which have not been previously reported in Antarctic
notothenioid fish. 相似文献
955.
956.
Kondo Y Tokuda N Fan X Yamashita T Honke K Takematsu H Takematsu H Togayachi A Ohta M Kotzusumi Y Narimatsu H Tajima O Furukawa K Furukaw K Furukawa K 《Biochemical and biophysical research communications》2009,378(2):179-181
Certain glycosphingolipids play important roles as cellular receptor for bacterial toxins with high specificity and strong affinity. In particular AB(5) toxins exhibit typical modes of cell attachment with B5 and invasion and biological effects in cells with A subunit. Subtilase cytotoxin (SubAB) is the prototype of a recently discovered AB(5) cytotoxin family produced by certain strains of Shiga toxigenic Escherichia coli, and shows highly specific serine protease activity toward endoplasmic reticulum chaperone Bip. Since this toxin bound to a mimic of ganglioside GM2, GM2 has been considered to be possible receptor for SubAB. Using six kinds of glycosylation-defective knockout mice lacking certain group of glycosphingolipids, sensitivity to SubAB in vivo was analyzed. Consequently, all mutant mice died at around 70h after intraperitoneal injection of 10 microg (or 7.5 microg) of SubAB as well as wild type mice. These results indicated none of glycolipids are not pivotal receptor for SubAB in the body. 相似文献
957.
958.
Hideyuki Kawabata Taro Katsura Eiji Kondo Nobuto Kitamura Shin Miyatake Yoshie Tanabe Takao Setoguchi Setsuro Komiya Kazunori Yasuda 《Journal of biomechanics》2009,42(15):2611-2615
The effect of stress deprivation on the tendon tissue has been an important focus in the field of biomechanics. However, less is known about the in vivo effect of stress deprivation on fibroblast apoptosis as of yet. This study was conducted to test a hypothesis that complete stress deprivation of the patellar tendon induces fibroblast apoptosis in vivo with activation of Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38) within 24 h after treatment. A total of 35 mature rabbits were divided into stress-shielded (n=15), sham-operated (n=15), and control (n=5) groups. To completely shield the patellar tendon from stress, we used an established surgical method. Animals were sacrificed at 24 h, and 2, 4, 7, and 14 days after the treatment. Tendon specimens underwent TUNEL assay and immunohistological examinations of active caspase-3, JNK, and p38. Both the number and the ratio of TUNEL-positive and caspase-3-positive cells were significantly greater (p<0.0001) in the stress-shielded group than in the sham group at 24 h, 2, 4, and 7 days. Concerning JNK and p38, both the number and the ratio were significantly greater (p<0.0001) in the stress-shielded group than in the sham group at 24 h, 2, and 4 days. This study demonstrated that complete stress deprivation induces fibroblast apoptosis in vivo with activation of JNK and p38 within 24 h. This fact suggested that the fibroblast apoptosis caused by stress deprivation is induced via the mitogen-activated protein kinase signaling pathway. 相似文献
959.
Naomi J. Marty Dakshinamurthy Rajalingam Alicia D. Kight Nathaniel E. Lewis Daniel Fologea Thallapuranam Krishnaswamy Suresh Kumar Ralph L. Henry Robyn L. Goforth 《The Journal of biological chemistry》2009,284(22):14891-14903
The chloroplast signal recognition particle (cpSRP) and its receptor
(cpFtsY) function in thylakoid biogenesis to target integral membrane proteins
to thylakoids. Unlike cytosolic SRP receptors in eukaryotes, cpFtsY partitions
between thylakoid membranes and the soluble stroma. Based on sequence
alignments, a membrane-binding motif identified in Escherichia coli
FtsY appears to be conserved in cpFtsY, yet whether the proposed motif is
responsible for the membrane-binding function of cpFtsY has yet to be shown
experimentally. Our studies show that a small N-terminal region in cpFtsY
stabilizes a membrane interaction critical to cpFtsY function in
cpSRP-dependent protein targeting. This membrane-binding motif is both
necessary and sufficient to direct cpFtsY and fused passenger proteins to
thylakoids. Our results demonstrate that the cpFtsY membrane-binding motif may
be functionally replaced by the corresponding region from E. coli,
confirming that the membrane-binding motif is conserved among organellar and
prokaryotic homologs. Furthermore, the capacity of cpFtsY for lipid binding
correlates with liposome-induced GTP hydrolysis stimulation. Mutations that
debilitate the membrane-binding motif in cpFtsY result in higher rates of GTP
hydrolysis, suggesting that negative regulation is provided by the intact
membrane-binding region in the absence of a bilayer. Furthermore, NMR and CD
structural studies of the N-terminal region and the analogous region in the
E. coli SRP receptor revealed a conformational change in secondary
structure that takes place upon lipid binding. These studies suggest that the
cpFtsY membrane-binding motif plays a critical role in the intramolecular
communication that regulates cpSRP receptor functions at the membrane.Proper compartmentalization of proteins relies on the ability of protein
localization pathways to transport proteins efficiently from their sites of
synthesis to their sites of function. The signal recognition particle
(SRP)2 and its
receptor function in every kingdom of life to target proteins to the
endoplasmic reticulum (eukaryotes), cytoplasmic membrane (prokaryotes), and
thylakoid membrane (chloroplasts)
(1). The targeting function of
SRP relies on a conserved 54-kDa SRP subunit (SRP54; Ffh in Escherichia
coli and cpSRP54 in chloroplasts) as well as a conserved SRP receptor
(SRα; FtsY in E. coli and cpFtsY in chloroplasts). For
cytosolic SRPs (SRP54 and Ffh), interactions with a substrate signal sequence
and an SRP RNA moiety are prerequisite for interaction with the SRP receptor
(SRα and FtsY) (2). GTP
binding and hydrolysis by both SRP54 and SRα coordinate substrate
release from SRP to the translocon and release of SRP from SRα. In
chloroplasts, cpFtsY functions along with a unique SRP (cpSRP) to
post-translationally target nuclear encoded proteins to thylakoid membranes
(3). Light-harvesting
chlorophyll a/b-binding proteins (LHCPs) imported into the
chloroplast stroma are bound by cpSRP to form a soluble targeting complex,
which directs the LHCP substrate to the thylakoid membrane translocon Alb3
(Albino3) in a GTP- and cpFtsY-dependent manner
(14,
36). Although many general
steps of SRP protein targeting seem largely conserved across evolutionary
boundaries, the nature and dynamics of the receptor appear to have
diverged.In eukaryotic systems, SRα is peripherally bound to the membrane
through association with the integral membrane subunit SRβ. In contrast,
no chloroplast or bacterial homolog of SRβ has been identified. cpFtsY
and E. coli FtsY (EcFtsY) are found partitioned between the membrane
and the stroma or cytosol, respectively. The membrane-binding capacity of
EcFtsY serves to stimulate GTPase activity and appears critical in that only
membrane-associated EcFtsY supports the release of nascent chains from SRP to
the translocon (4,
5). However, the partitioning
activity is not strictly required because EcFtsY tethered to the membrane is
functional in vivo
(37). Given the conserved
nature of partitioning among bacterial and chloroplast SRP receptors,
partitioning may play an, as of yet, unidentified role in protein targeting by
SRP. Nevertheless, differences in lipid composition between bacterial and
thylakoid membranes make it interesting to speculate that there are
mechanistic differences in membrane partitioning.Like many prokaryotic FtsY homologs (e.g. Thermus aquaticus),
cpFtsY lacks the N-terminal acidic domain (A domain) implicated in EcFtsY
membrane binding (6). Although
the highly conserved FtsY GTPase domain (NG domain) of EcFtsY
(EcFtsYNG) fails to support protein targeting, the addition of the
last A domain residue, Phe-196 of a conserved double-Phe motif
(EcFtsYNG+1), restores protein targeting in vivo
(7). In vitro studies
also show that EcFtsYNG+1 retains the capacity to bind membranes
and support integration of SRP-dependent substrates, although at significantly
reduced levels compared with full-length EcFtsY
(8). A resolved structure of
EcFtsYNG+1 suggests that the amphipathic nature of the region
containing Phe-196 plays a critical role in membrane association
(9). Furthermore, it has been
demonstrated that liposomes stimulate GTP hydrolysis rates of SRP with
EcFtsYNG+1, but not with EcFtsYNG, supporting the idea
that the A domain in its entirety is not strictly required.For cpFtsY, the necessity and functional role(s) of partitioning between a
thylakoid-bound and a soluble phase, as well as the role of N-terminal
residues in these functions, remain unknown. In addition, both the
conformational state of membrane-bound cpFtsY and EcFtsY and the mechanism
responsible for controlling membrane partitioning and altered GTPase activity
remain unclear. Because of the gain of function exhibited by
EcFtsYNG+1 and the conserved nature of the surrounding motif
(9), it seems likely that this
conserved region is necessary to support membrane binding and corresponding
functions not only in EcFtsY but also in FtsY homologs.To examine the functional role of the N-terminal region of cpFtsY, we have
utilized deletion and point mutants in assays that reconstitute cpFtsY
activities, including the cpSRP-dependent integration of LHCP. Together, our
data indicate that the conserved lipid-binding motif identified in bacterial
FtsY homologs is present in cpFtsY and is both necessary and sufficient for
thylakoid binding and critical for LHCP targeting. 相似文献