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991.
992.
Katsushi Kuroda Kana Yamashita Takeshi Fujiwara 《Trees - Structure and Function》2009,23(6):1163-1172
The mechanism of heartwood formation in Cryptomeria japonica D. Don has long been studied since heartwood formation is a fundamental physiological feature of trees. In this study, the
water distribution in the xylem of C. japonica was investigated at the cellular level to reveal the role of water distribution in the xylem during heartwood formation.
Samples were taken from different heights of each trunk, in which the phases of heartwood formation differed. These were designated
as SIH, which consisted of sapwood, intermediate wood, and heartwood; SI, which consisted of sapwood and intermediate wood
but no heartwood; and S-all, which consisted entirely of sapwood. Cryo-scanning electron microscopic observations of the heartwood-formed
(SIH) and non-heartwood-formed (SI and S-all) xylem revealed different patterns of water distribution changes in tracheids
between the latewood and earlywood. In the latewood, almost all tracheids were filled with water in all areas from the sapwood
to the heartwood (98–100% of tracheids had water in their lumina). In the earlywood, however, the water distribution differed
between the sapwood (95–99%), intermediate wood (7–12%), and heartwood (4–100%). Many of the tracheids in the xylem, where
the sapwood changed to intermediate wood lost water. In the heartwood, some tracheids remained empty, while others were refilled
with water. These results suggest that the water distribution changes in individual tracheids are closely related to heartwood
formation. Water loss from tracheids may be an important factor inducing heartwood formation in the xylem of C. japonica. 相似文献
993.
994.
Mitogen-Activated Protein Kinase-Activated Kinase RSK2 Plays a Role in Innate Immune Responses to Influenza Virus Infection 下载免费PDF全文
995.
996.
997.
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
998.
Ayako Fukunaka Tomoyuki Suzuki Yayoi Kurokawa Tomohiro Yamazaki Naoko Fujiwara Kaori Ishihara Hitoshi Migaki Katsuzumi Okumura Seiji Masuda Yuko Yamaguchi-Iwai Masaya Nagao Taiho Kambe 《The Journal of biological chemistry》2009,284(45):30798-30806
The majority of CDF/ZnT zinc transporters form homo-oligomers. However, ZnT5, ZnT6, and their orthologues form hetero-oligomers in the early secretory pathway where they load zinc onto zinc-requiring enzymes and maintain secretory pathway functions. The details of this hetero-oligomerization remain to be elucidated, and much more is known about homo-oligomerization that occurs in other CDF/ZnT family proteins. Here, we addressed this issue using co-immunoprecipitation experiments, mutagenesis, and chimera studies of hZnT5 and hZnT6 in chicken DT40 cells deficient in ZnT5, ZnT6, and ZnT7 proteins. We found that hZnT5 and hZnT6 combine to form heterodimers but do not form complexes larger than heterodimers. Mutagenesis of hZnT6 indicated that the sites present in transmembrane domains II and V in which many CDF/ZnT proteins have conserved hydrophilic amino acid residues are not involved in zinc binding of hZnT6, although they are required for zinc transport in other CDF/ZnT family homo-oligomers. We also found that the long N-terminal half of hZnT5 is not necessary for its functional interaction with hZnT6, whereas the cytosolic C-terminal tail of hZnT5 is important in determining hZnT6 as a partner molecule for heterodimer formation. In DT40 cells, cZnT5 variant lacking the N-terminal half was endogenously induced during periods of endoplasmic reticulum stress and so seemed to function to supply zinc to zinc-requiring enzymes under these conditions. The results outlined here provide new information about the mechanism of action through heterodimerization of CDF/ZnT proteins that function in the early secretory pathway. 相似文献
999.
Saori Hata Sayaka Fujishige Yoichi Araki Naoko Kato Masahiko Araseki Masaki Nishimura Dieter Hartmann Paul Saftig Falk Fahrenholz Miyako Taniguchi Katsuya Urakami Hiroyasu Akatsu Ralph N. Martins Kazuo Yamamoto Masahiro Maeda Tohru Yamamoto Tadashi Nakaya Sam Gandy Toshiharu Suzuki 《The Journal of biological chemistry》2009,284(52):36024-36033
Alcadeins (Alcs) constitute a family of neuronal type I membrane proteins, designated Alcα, Alcβ, and Alcγ. The Alcs express in neurons dominantly and largely colocalize with the Alzheimer amyloid precursor protein (APP) in the brain. Alcs and APP show an identical function as a cargo receptor of kinesin-1. Moreover, proteolytic processing of Alc proteins appears highly similar to that of APP. We found that APP α-secretases ADAM 10 and ADAM 17 primarily cleave Alc proteins and trigger the subsequent secondary intramembranous cleavage of Alc C-terminal fragments by a presenilin-dependent γ-secretase complex, thereby generating “APP p3-like” and non-aggregative Alc peptides (p3-Alcs). We determined the complete amino acid sequence of p3-Alcα, p3-Alcβ, and p3-Alcγ, whose major species comprise 35, 37, and 31 amino acids, respectively, in human cerebrospinal fluid. We demonstrate here that variant p3-Alc C termini are modulated by FAD-linked presenilin 1 mutations increasing minor β-amyloid species Aβ42, and these mutations alter the level of minor p3-Alc species. However, the magnitudes of C-terminal alteration of p3-Alcα, p3-Alcβ, and p3-Alcγ were not equivalent, suggesting that one type of γ-secretase dysfunction does not appear in the phenotype equivalently in the cleavage of type I membrane proteins. Because these C-terminal alterations are detectable in human cerebrospinal fluid, the use of a substrate panel, including Alcs and APP, may be effective to detect γ-secretase dysfunction in the prepathogenic state of Alzheimer disease subjects. 相似文献
1000.
Luo X Okubo T Randell S Hogan BL 《In vitro cellular & developmental biology. Animal》2009,45(1-2):44-54
The tongue represents a very accessible source of tissue-specific epithelial stem cells of endodermal origin. However, little is known about the properties of these cells and the mechanisms regulating their proliferation and differentiation. Foxa2, an endodermal marker, is expressed throughout the tongue epithelium during embryonic development but becomes confined to a minority of basal cells and some taste bud sensory cells in the adult tongue. Using a previously described line of transgenic mice in which enhanced green fluorescent protein (eGFP) is expressed under the control of a human keratin 5 promoter region (Krt5-eGFP), we have isolated a subpopulation of cells in the basal epithelial layer of the mouse tongue with a high efficiency of generating holoclones of undifferentiated cells in culture with a feeder layer. Krt5-GFP(hi) cells can both self renew and give rise to differentiated stratified keratinized epithelial cells when cultured on an air-liquid interface. 相似文献