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31.
Diurnal changes in needle gas exchange in alpine Pinus pumila during snow-melting and summer seasons
Atsushi Ishida Takashi Nakano Seikoh Sekikawa Emiko Maruta Takehiro Masuzawa 《Ecological Research》2001,16(1):107-116
Pinus pumila (Pallas) Regel. is a dominant dwarf tree in alpine regions of Japan. The possible factors limiting the net photosynthetic rate (Pn) of the needles of P. pumila were examined in the snow-melting (May) and the summer (August) seasons. In August, in situ maximum Pn was 20 mol kg–1 needle s–1 in the current-year needles and 25 mol kg–1 needle s–1 in the 1-year-old needles. Diurnal trends of Pn in August were positively related to fluctuations in photosynthetic photon flux density (PPFD) and no midday depression of Pn was found, indicating that a decrease in PPFD rather than an increase in needle-to-air vapor pressure deficit (W) might cause the reduction of Pn. Both stomatal conductance (gs) and Pn were lower in May than in August. In May, Pn and gs were almost zero in the morning, but gradually increased with decreasing W, reaching maximum Pn values (4 mol kg–1 needle s–1) and gs (60 mmol kg–1 needle s–1) at 16.00 hours. The daytime Pn in May was positively related to gs. Relative water content in the exposed needles above the snow in May was 83%, which was far above the lethal level. This indicates that the water flow from stems or soils to needles was enough to compensate for a small amount of water loss due to the low gs in May, although the water supplied to needles would be impeded by the low temperatures. Thus, the reduced gs in May would be important for avoiding needle desiccation, and would result in a reduced Pn. 相似文献
32.
Hosoi T Koguchi Y Sugikawa E Chikada A Ogawa K Tsuda N Suto N Tsunoda S Taniguchi T Ohnuki T 《The Journal of biological chemistry》2002,277(35):31459-31465
33.
Futami J Nukui E Maeda T Kosaka M Tada H Seno M Yamada H 《Journal of biochemistry》2002,132(2):223-228
Cationization of a protein is considered to be a powerful strategy for internalizing a functional protein into cells. Cationized proteins appear to adsorb to the cell surface by electrostatic interactions, then enter the cell in a receptor- and transporter-independent fashion. Thus, in principle, all cell types appear to take up cationized proteins. Since ribonucleases (RNases) have a latent cytotoxic potential, cationized RNases could be useful cancer chemotherapeutics. In this study, we investigated the effect of the degree of cationization on the cytotoxicity of RNase A by modifying carboxyl groups with ethylenediamine. We found that there is an optimum degree of modification for cytotoxicity, in which 5 to 7 out of 11 carboxyl groups in RNase A are modified, toward MCF-7 and 3T3-SV-40 cells. More interestingly, the cytotoxicity of cationized RNase As correlates well with the value of [RNase activity] x [estimated concentration of RNase free from RNase inhibitor], mimicking the practical enzymatic activity of cationized RNase As in cytosol. The results indicate that cationization of a protein to an optimum level is important for maintaining protein function in the cytosol. Sophisticated protein cationization techniques will help to advance protein transduction technology. 相似文献
34.
Two flavonoid glucosyltransferases from Petunia hybrida: molecular cloning,biochemical properties and developmentally regulated expression 总被引:4,自引:0,他引:4
Yamazaki M Yamagishi E Gong Z Fukuchi-Mizutani M Fukui Y Tanaka Y Kusumi T Yamaguchi M Saito K 《Plant molecular biology》2002,48(4):401-411
Two flavonoid glucosyltransferases, UDP-glucose:flavonoid 3-O-glucosyltransferase (3-GT) and UDP-glucose: anthocyanin 5-O-glucosyltransferase (5-GT), are responsible for the glucosylation of anthocyani(di)ns to produce stable molecules in the anthocyanin biosynthetic pathway. The cDNAs encoding 3-GT and 5-GT were isolated from Petunia hybrida by hybridization screening with heterologous probes. The cDNA clones of 3-GT, PGT8, and 5-GT, PH1, encode putative polypeptides of 448 and 468 amino acids, respectively. A phylogenetic tree based on amino acid sequences of the family of glycosyltransferases from various plants shows that PGT8 belongs to the 3-GT subfamily and PH1 belongs to the 5-GT subfamily. The function of isolated cDNAs was identified by the catalytic activities for 3-GT and 5-GT exhibited by the recombinant proteins produced in yeast. The recombinant PGT8 protein could convert not only anthocyanidins but also flavonols into the corresponding 3-O-glucosides. In contrast, the recombinant PH1 protein exhibited a strict substrate specificity towards anthocyanidin 3-acylrutinoside, comparing with other 5-GTs from Perilla frutescens and Verbena hybrida, which showed broad substrate specificities towards several anthocyanidin 3-glucosides. The mRNA expression of both 3-GT and 5-GT increased in the early developmental stages of P. hybrida flower, reaching the maximum at the stage before flower opening. Southern blotting analysis of genomic DNA indicates that both 3-GT and 5-GT genes exist in two copies in P. hybrida, respectively. The results are discussed in relation to the molecular evolution of flavonoid glycosyltransferases. 相似文献
35.
36.
Yamamoto H Yamauchi E Taniguchi H Ono T Miyamoto E 《Archives of biochemistry and biophysics》2002,408(2):255-262
The paired helical filaments (PHF) found in Alzheimer's disease (AD) brain are composed mainly of the hyperphosphorylated form of microtubule-associated protein tau (PHF-tau). It is well known that tau is a good in vitro substrate for Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II). To establish the phosphorylation sites, the longest human tau (hTau40) was bacterially expressed and phosphorylated by CaM kinase II, followed by digestion with lysyl endoprotease. The digests were subjected to liquid chromatography/mass spectrometry. We found that 5 of 22 identified peptides were phosphorylated. From the tandem mass spectrometry, two phosphorylation sites (serines 262 and 356) were identified in the tubulin binding sites. When tau was phosphorylated by CaM kinase II, the binding of tau to taxol-stabilized microtubules was remarkably impaired. As both serines 262 and 356 are reportedly phosphorylated in PHF-tau, CaM kinase II may be involved in hyperphosphorylation of tau in AD brain. 相似文献
37.
Nosaka T Morita S Kitamura H Nakajima H Shibata F Morikawa Y Kataoka Y Ebihara Y Kawashima T Itoh T Ozaki K Senba E Tsuji K Makishima F Yoshida N Kitamura T 《Molecular and cellular biology》2003,23(8):2969-2980
Dorsoventral patterning depends on the local concentrations of the morphogens. Twisted gastrulation (TSG) regulates the extracellular availability of a mesoderm inducer, bone morphogenetic protein 4 (BMP-4). However, TSG function in vivo is still unclear. We isolated a TSG cDNA as a secreted molecule from the mouse aorta-gonad-mesonephros region. Here we show that TSG-deficient mice were born healthy, but more than half of the neonatal pups showed severe growth retardation shortly after birth and displayed dwarfism with delayed endochondral ossification and lymphopenia, followed by death within a month. TSG-deficient thymus was atrophic, and phosphorylation of SMAD1 was augmented in the thymocytes, suggesting enhanced BMP-4 signaling in the thymus. Since BMP-4 promotes skeletogenesis and inhibits thymus development, our findings suggest that TSG acts as both a BMP-4 agonist in skeletogenesis and a BMP-4 antagonist in T-cell development. Although lymphopenia in TSG-deficient mice would partly be ascribed to systemic effects of runtiness and wasting, our findings may also provide a clue for understanding the pathogenesis of human dwarfism with combined immunodeficiency. 相似文献
38.
Rosenberg EY Bertenthal D Nilles ML Bertrand KP Nikaido H 《Molecular microbiology》2003,48(6):1609-1619
AcrAB of Escherichia coli, an archetype among bacterial multidrug efflux pumps, exports an extremely wide range of substrates including solvents, dyes, detergents and antimicrobial agents. Its expression is regulated by three XylS/AraC family regulators, MarA, SoxS and Rob. Although MarA and SoxS regulation works by the alteration of their own expression levels, it was not known how Rob, which is constitutively expressed, exerts its regulatory action. We show here that the induction of the AcrAB efflux pump by decanoate and the more lipophilic unconjugated bile salts is mediated by Rob, and that the low-molecular-weight inducers specifically bind to the C-terminal, non-DNA-binding domain of Rob. Induction of Rob is not needed for induction of AcrAB, and we suggest that the inducers act by producing conformational alterations in pre-existing Rob, as was suggested recently (Rosner, Dangi, Gronenborn and Martin, J Bacteriol 184: 1407-1416, 2002). Decanoate and unconjugated bile salts, which are present in the normal habitat of E. coli, were further shown to make the bacteria more resistant to lipophilic antibiotics, at least in part because of the induction of the AcrAB efflux pump. Thus, it is likely that E. coli is protecting itself by the Rob-mediated upregulation of AcrAB against the harmful effects of bile salts and fatty acids in the intestinal tract. 相似文献
39.
We studied the synergistic effects of Japanese green tea extract (JGTE) and levofloxacin (LVFX) against enterohemorrhagic
Escherichia coli (EHEC) infection in a gnotobiotic mouse model. Mice fed on JGTE conferred a significant degree of protection against an oral
challenge with EHEC. Complete elimination of the bacteria from the mice, was however, difficult. The combination of JGTE and
LVFX increased the survival rate and reduced damage to target organs. Thus, dietary supplementation with JGTE improved the
therapeutic effects of antibiotic treatment.
Received: 28 July 2000 / Accepted: 19 September 2000 相似文献
40.
We have isolated a novel human cDNA coding for human salt-tolerant protein (HSTP), that is a homologue of the rat salt-tolerant
protein (STP) and may contribute to salt-induced hypertension by modulating renal cation transport. The nucleotide sequence
(1988 bp) of the HSTP cDNA contains an open reading frame encoding a polypeptide comprising 545 amino acids, two residues
fewer than the rat STP cDNA. The predicted amino acid sequence exhibits 92% identity to that of the rat protein. HSTP contains
predicted coiled-coil domains and Src Homology 3 domain, and shows a high degree of identity to CIP4 (Cdc42 target protein)
and human Trip 10 (thyroid-hormone receptor interacting protein). We have mapped the HSTPgene to human chromosome 19 by fluorescence in situhybridization.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献