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121.
122.
Calmodulin is known to transduce Ca2+ signals by interacting with specific target proteins. In order to determine the role of calmodulin in regulating neuronal
survival and death, we examined, whether calmodulin inhibitors induce caspase-dependent apoptotic cell death, and whether
glycogen synthase kinase-3 is involved in calmodulin inhibitor-induced cell death in PC12 cells. W13, a calmodulin specific
inhibitor increased apoptotic cell death with morphological changes characterized by cell shrinkage and nuclear condensation
of fragmentation. Glycogen synthase kinase-3 inhibitors prevented calmodulin inhibitor-induced apoptosis. In addition, nerve
growth factor and cycloheximide, a protein synthesis inhibitor, completely blocked cell death. Moreover, caspase-3 activation
was accompanied by calmodulin inhibitor-induced cell death and inhibited by nerve growth factor. These results suggest that
calmodulin inhibitors induce caspase-dependent apoptosis, and the activation of glycogen synthase kinase-3 is involved in
the death of PC12 cells. 相似文献
123.
Yamada H Tamada T Kosaka M Miyata K Fujiki S Tano M Moriya M Yamanishi M Honjo E Tada H Ino T Yamaguchi H Futami J Seno M Nomoto T Hirata T Yoshimura M Kuroki R 《Protein science : a publication of the Protein Society》2007,16(7):1389-1397
A protein crystal lattice consists of surface contact regions, where the interactions of specific groups play a key role in stabilizing the regular arrangement of the protein molecules. In an attempt to control protein incorporation in a crystal lattice, a leucine zipper-like hydrophobic interface (comprising four leucine residues) was introduced into a helical region (helix 2) of the human pancreatic ribonuclease 1 (RNase 1) that was predicted to form a suitable crystallization interface. Although crystallization of wild-type RNase 1 has not yet been reported, the RNase 1 mutant having four leucines (4L-RNase 1) was successfully crystallized under several different conditions. The crystal structures were subsequently determined by X-ray crystallography by molecular replacement using the structure of bovine RNase A. The overall structure of 4L-RNase 1 is quite similar to that of the bovine RNase A, and the introduced leucine residues formed the designed crystal interface. To characterize the role of the introduced leucine residues in crystallization of RNase 1 further, the number of leucines was reduced to three or two (3L- and 2L-RNase 1, respectively). Both mutants crystallized and a similar hydrophobic interface as in 4L-RNase 1 was observed. A related approach to engineer crystal contacts at helix 3 of RNase 1 (N4L-RNase 1) was also evaluated. N4L-RNase 1 also successfully crystallized and formed the expected hydrophobic packing interface. These results suggest that appropriate introduction of a leucine zipper-like hydrophobic interface can promote intermolecular symmetry for more efficient protein crystallization in crystal lattice engineering efforts. 相似文献
124.
Matsumoto Y Marusawa H Kinoshita K Endo Y Kou T Morisawa T Azuma T Okazaki IM Honjo T Chiba T 《Nature medicine》2007,13(4):470-476
Infection with Helicobacter pylori (H. pylori) is a risk factor for the development of gastric cancer. Here we show that infection of gastric epithelial cells with 'cag' pathogenicity island (cagPAI)-positive H. pylori induced aberrant expression of activation-induced cytidine deaminase (AID), a member of the cytidine-deaminase family that acts as a DNA- and RNA-editing enzyme, via the IkappaB kinase-dependent nuclear factor-kappaB activation pathway. H. pylori-mediated upregulation of AID resulted in the accumulation of nucleotide alterations in the TP53 tumor suppressor gene in gastric cells in vitro. Our findings provide evidence that aberrant AID expression caused by H. pylori infection might be a mechanism of mutation accumulation in the gastric mucosa during H. pylori-associated gastric carcinogenesis. 相似文献
125.
Mutsuo Ichinomiya Masaki Honda Haruto Shimoda Kenji Saito Tsuneo Odate Mitsuo Fukuchi Akira Taniguchi 《Polar Biology》2007,30(10):1285-1293
Temporal variations in the microbial community structure of plankton, which is composed of autotrophic and heterotrophic pico-,
nano- and microplankton, were investigated during the austral summer of 2005/2006 under fast ice near Syowa Station, eastern
Antarctica. Autotrophic algal populations were composed almost entirely of diatoms followed by phytoflagellates such as autotrophic
dinoflagellates and cryptophytes. Among the microbial community, heterotrophic biomass was dominated by heterotrophic dinoflagellates
and naked ciliates and finally exceeded autotrophic biomass. Qualitative microscopic analysis revealed that heterotrophic
dinoflagellates were ingesting large number of diatoms. Synchronizing fluctuation of naked ciliates with phytoflagellates
suggested a predator–prey relationship between them. Our results suggest that the pelagic food webs under the extensive ice-covered
areas in coastal Antarctic regions are not short but complex. 相似文献
126.
Intra- and transcellular water movements in plants are regulated by the water permeability of the plasma membrane (PM) and vacuolar membrane (VM) in plant cells. In the present study, we investigated the osmotic water permeability of both PM (P ( f1)) and VM (P ( f2)), as well as the bulk osmotic water permeability of a protoplast (P ( f(bulk))) isolated from radish (Raphanus sativus) roots. The values of P ( f(bulk)) and P ( f2) were determined from the swelling/shrinking rate of protoplasts and isolated vacuoles under hypo- or hypertonic conditions. In order to minimize the effect of unstirred layer, we monitored dropping or rising protoplasts (vacuoles) in sorbitol solutions as they swelled or shrunk. P ( f1) was calculated from P ( f(bulk)) and P ( f2) by using the 'three-compartment model', which describes the theoretical relationship between P ( f1), P ( f2) and P ( f(bulk)) (Kuwagata and Murai-Hatano in J Plant Res, 2007). The time-dependent changes in the volume of protoplasts and isolated vacuoles fitted well to the theoretical curves, and solute permeation of PM and VM was able to be neglected for measuring the osmotic water permeability. High osmotic water permeability of more than 500 mum s(-1), indicating high activity of aquaporins (water channels), was observed in both PM and VM in radish root cells. This method has the advantage that P ( f1) and P ( f2) can be measured accurately in individual higher plant cells. 相似文献
127.
128.
Takeshi Hiromoto Eijiro Honjo Naonobu Noda Taro Tamada Kohei Kazuma Masahiko Suzuki Michael Blaber Ryota Kuroki 《Protein science : a publication of the Protein Society》2015,24(3):395-407
UDP‐glucose: anthocyanidin 3‐O‐glucosyltransferase (UGT78K6) from Clitoria ternatea catalyzes the transfer of glucose from UDP‐glucose to anthocyanidins such as delphinidin. After the acylation of the 3‐O‐glucosyl residue, the 3′‐ and 5′‐hydroxyl groups of the product are further glucosylated by a glucosyltransferase in the biosynthesis of ternatins, which are anthocyanin pigments. To understand the acceptor‐recognition scheme of UGT78K6, the crystal structure of UGT78K6 and its complex forms with anthocyanidin delphinidin and petunidin, and flavonol kaempferol were determined to resolutions of 1.85 Å, 2.55 Å, 2.70 Å, and 1.75 Å, respectively. The enzyme recognition of unstable anthocyanidin aglycones was initially observed in this structural determination. The anthocyanidin‐ and flavonol‐acceptor binding details are almost identical in each complex structure, although the glucosylation activities against each acceptor were significantly different. The 3‐hydroxyl groups of the acceptor substrates were located at hydrogen‐bonding distances to the Nε2 atom of the His17 catalytic residue, supporting a role for glucosyl transfer to the 3‐hydroxyl groups of anthocyanidins and flavonols. However, the molecular orientations of these three acceptors are different from those of the known flavonoid glycosyltransferases, VvGT1 and UGT78G1. The acceptor substrates in UGT78K6 are reversely bound to its binding site by a 180° rotation about the O1–O3 axis of the flavonoid backbones observed in VvGT1 and UGT78G1; consequently, the 5‐ and 7‐hydroxyl groups are protected from glucosylation. These substrate recognition schemes are useful to understand the unique reaction mechanism of UGT78K6 for the ternatin biosynthesis, and suggest the potential for controlled synthesis of natural pigments. 相似文献
129.
Life history strategy and adult and larval behavior of Macrodiplosis selenis (Diptera: Cecidomyiidae), a species that induces leaf‐margin fold galls on deciduous Quercus (Fagaceae) 下载免费PDF全文
Wanggyu Kim Kiyoko Matsunaga Naohisa Gyoutoku Kazunori Matsuo Tsuneo Minami Junichi Yukawa 《Entomological Science》2015,18(4):470-478
Life historical, behavioral and ecological traits of Macrodiplosis selenis, which induces leaf‐margin fold galls on Quercus serrata, Q. mongolica and Q. dentata (Fagaceae) in Japan and South Korea, were studied. Daily activity and larval development indicate that M. selenis is a diurnal and univoltine gall midge. In April, females lay their eggs both on upper and under surfaces of fresh leaves. The duration of the egg stage varies from 5 to 9 days, depending on daily temperatures. Hatched larvae crawl to the upper surface of the leaf margin, where they start to induce galls. Larvae become full‐grown in October, drop to the ground in November and overwinter in cocoons on the ground, while larvae of congeners mature in May and drop to the ground in June. A relatively long period of the second larval stadium from July to October on the host trees seems to be effective for M. selenis in avoiding summer mortalities caused by predation and aridity on the ground and by ectoparasitoids that attack mature larvae or pupae on the host leaves. The spatial distribution pattern of M. selenis leaf galls is contagious and the mean gall density per leaf is significantly correlated with the mean crowding. This study adds new insights of life history strategy and adult and larval behavioral pattern to the ecological knowledge of gall midges, and these kinds of information are essential for further studies of M. selenis population dynamics and interactions with other Quercus‐associated herbivores. 相似文献
130.
We describe the synthesis of 11C-labeled α-aminoisobutyric acid 2 from iodo[11C]methane and methyl N-(diphenylmethylen)-d,l-alaniate (5). The tetrabutylammonium fluoride (TBAF)-promoted α-[11C]methylation of sterically hindered analog 5 was a key step in our synthesis process. Total radiochemical conversion of 2 was high and a remote-controlled synthesis was carried out. A comparative tumor positron emission tomography (PET) imaging study using the same model mouse showed higher uptake of 2 than with 11C-labeled methionine and [18F] fluorodeoxyglucose (FDG). 相似文献