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Cross-linking reovirus spike protein with the bifunctional reagent dimethyl suberimidate revealed that each spike was composed of a pentameric aggregate of polypeptide lambda 2. 相似文献
105.
Phosphorylation on tyrosine-15 of p34(Cdc2) by ErbB2 inhibits p34(Cdc2) activation and is involved in resistance to taxol-induced apoptosis 总被引:4,自引:0,他引:4
Tan M Jing T Lan KH Neal CL Li P Lee S Fang D Nagata Y Liu J Arlinghaus R Hung MC Yu D 《Molecular cell》2002,9(5):993-1004
ErbB2 overexpression confers resistance to taxol-induced apoptosis by inhibiting p34(Cdc2) activation. One mechanism is via ErbB2-mediated upregulation of p21(Cip1), which inhibits Cdc2. Here, we report that the inhibitory phosphorylation on Cdc2 tyrosine (Y)15 (Cdc2-Y15-p) is elevated in ErbB2-overexpressing breast cancer cells and primary tumors. ErbB2 binds to and colocalizes with cyclin B-Cdc2 complexes and phosphorylates Cdc2-Y15. The ErbB2 kinase domain is sufficient to directly phosphorylate Cdc2-Y15. Increased Cdc2-Y15-p in ErbB2-overexpressing cells corresponds with delayed M phase entry. Expressing a nonphosphorylatable mutant of Cdc2 renders cells more sensitive to taxol-induced apoptosis. Thus, ErbB2 membrane RTK can confer resistance to taxol-induced apoptosis by directly phosphorylating Cdc2. 相似文献
106.
Downregulation of p‐COUMAROYL ESTER 3‐HYDROXYLASE in rice leads to altered cell wall structures and improves biomass saccharification 下载免费PDF全文
Yuri Takeda Yuki Tobimatsu Steven D. Karlen Taichi Koshiba Shiro Suzuki Masaomi Yamamura Shinya Murakami Mai Mukai Takefumi Hattori Keishi Osakabe John Ralph Masahiro Sakamoto Toshiaki Umezawa 《The Plant journal : for cell and molecular biology》2018,95(5):796-811
p‐Coumaroyl ester 3‐hydroxylase (C3′H) is a key enzyme involved in the biosynthesis of lignin, a phenylpropanoid polymer that is the major constituent of secondary cell walls in vascular plants. Although the crucial role of C3′H in lignification and its manipulation to upgrade lignocellulose have been investigated in eudicots, limited information is available in monocotyledonous grass species, despite their potential as biomass feedstocks. Here we address the pronounced impacts of C3′H deficiency on the structure and properties of grass cell walls. C3′H‐knockdown lines generated via RNA interference (RNAi)‐mediated gene silencing, with about 0.5% of the residual expression levels, reached maturity and set seeds. In contrast, C3′H‐knockout rice mutants generated via CRISPR/Cas9‐mediated mutagenesis were severely dwarfed and sterile. Cell wall analysis of the mature C3′H‐knockdown RNAi lines revealed that their lignins were largely enriched in p‐hydroxyphenyl (H) units while being substantially reduced in the normally dominant guaiacyl (G) and syringyl (S) units. Interestingly, however, the enrichment of H units was limited to within the non‐acylated lignin units, with grass‐specific γ‐p‐coumaroylated lignin units remaining apparently unchanged. Suppression of C3′H also resulted in relative augmentation in tricin residues in lignin as well as a substantial reduction in wall cross‐linking ferulates. Collectively, our data demonstrate that C3′H expression is an important determinant not only of lignin content and composition but also of the degree of cell wall cross‐linking. We also demonstrated that C3′H‐suppressed rice displays enhanced biomass saccharification. 相似文献
107.
Barbara M. Croes William F. Laurance Sally A. Lahm Landry Tchignoumba Alfonso Alonso Michelle E. Lee Patrick Campbell Ralph Buij 《Biotropica》2007,39(2):257-263
Many animals can adjust their behavioral strategies to reduce predation risk. We investigated whether rain forest monkeys and duikers alter their antipredatory behavior in response to hunting by humans in southwestern Gabon. We compared monkey and duiker responses to human observers in an area where hunting is prohibited, to those in a nearby area where hunting pressure is moderate but spatially variable. The results of our study indicate that monkeys become more secretive when hunted, commencing alarm calls only when at a certain distance (typically > 50 m) from humans. We found no difference in monkey group size between hunted and no-hunting areas. In no-hunting areas, duikers often freeze in response to approaching observers, but in hunted areas they abandon this strategy and rapidly flee from humans. Duikers also whistle more often in areas where they are hunted frequently. Our findings have at least two important implications. First, behavioral observations of monkeys and duikers may be useful in gauging local hunting intensity in African rain forests. Second, duiker densities are likely to be overestimated in hunted areas, where they more readily flee and whistle, and underestimated in no-hunting areas, where they rely on freezing behavior to avoid detection. Because behavioral adaptations to hunting vary both among species and localities, these differences should be considered when attempting to derive population-density estimates for forest wildlife. 相似文献
108.
Repression of lignin biosynthesis promotes cellulose accumulation and growth in transgenic trees. 总被引:40,自引:0,他引:40
W J Hu S A Harding J Lung J L Popko J Ralph D D Stokke C J Tsai V L Chiang 《Nature biotechnology》1999,17(8):808-812
Because lignin limits the use of wood for fiber, chemical, and energy production, strategies for its downregulation are of considerable interest. We have produced transgenic aspen (Populus tremuloides Michx.) trees in which expression of a lignin biosynthetic pathway gene Pt4CL1 encoding 4-coumarate:coenzyme A ligase (4CL) has been downregulated by antisense inhibition. Trees with suppressed Pt4CL1 expression exhibited up to a 45% reduction of lignin, but this was compensated for by a 15% increase in cellulose. As a result, the total lignin-cellulose mass remained essentially unchanged. Leaf, root, and stem growth were substantially enhanced, and structural integrity was maintained both at the cellular and whole-plant levels in the transgenic lines. Our results indicate that lignin and cellulose deposition could be regulated in a compensatory fashion, which may contribute to metabolic flexibility and a growth advantage to sustain the long-term structural integrity of woody perennials. 相似文献
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110.
Manganese peroxidase (Mn peroxidase) catalyses the oxidation of Mn(II) to Mn(III), a diffusible non-specific oxidant likely
to be involved in the transformation of polyphenolic macromolecules from brown coal by the white-rot fungus Phanerochaete chrysosporium. We report here that solubilised macromolecules from Morwell brown coal were depolymerised by Mn(III) ions when incubated
under hyperbaric O2. However, under N2 or air they were polymerised, suggesting that net depolymerisation by Mn(III) requires molecular oxygen to inhibit coupling
of coal radicals. Coal macromolecules were also polymerised when separated by a semipermeable membrane from a culture of P. chrysosporium or from a solution of Mn peroxidase, Mn(II) and H2O2, probably by Mn(III) crossing the membrane. In oxygenated cultures in which Mn peroxidase␣was up-regulated by Mn(II), the
extent of depolymerisation correlated with cumulative Mn peroxidase activity suggesting that Mn-peroxidase-generated Mn(III)
has a central role in initial depolymerisation of coal molecules in vivo. However, mutant ME446-B17-1, which produces Mn peroxidase
but not lignin peroxidase, polymerised coal macromolecules in oxygenated cultures. In sum, it appears Mn peroxidase can both
polymerise and depolymerise brown coal macromolecules and that, in vivo, both hyperbaric O2 and lignin peroxidase are also required to force net depolymerisation to products assimilable by cells.
Received: 4 September 1997 / Received revision: 29 January 1998 / Accepted: 30 January 1998 相似文献