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排序方式: 共有207条查询结果,搜索用时 15 毫秒
1.
Characterization of phosphotyrosyl-protein phosphatase activity associated with calcineurin 总被引:3,自引:0,他引:3
J Chernoff M A Sells H C Li 《Biochemical and biophysical research communications》1984,121(1):141-148
Calcineurin purified from bovine brain is shown to possess phosphotyrosyl -protein phosphatase activity towards proteins phosphorylated by the epidermal growth factor receptor/kinase. The phosphatase activity is augmented by Ca2+/calmodulin or divalent cation (Ni2+ greater than Mn2+ greater than Mg2+ greater than Co2+). In the simultaneous presence of all three effectors, the enzymatic activity is synergistically increased. Ca2+/calmodulin activates the Mg2+-supported activity by decreasing the Km value for phosphotyrosyl -casein from 2.2 to 0.6 microM, and increasing the Vmax from 0.4 to 4.6 nmol/min/mg. These results represent the first demonstration that calcineurin can dephosphorylate phosphotyrosyl -proteins and suggest a novel mechanism of activation of this enzyme. 相似文献
2.
3.
D. A. Gordenin M. V. Trofimova O. N. Shaburova Y. I. Pavlov Y. O. Chernoff Y. V. Chekuolene Y. Y. Proscyavichus K. V. Sasnauskas A. A. Janulaitis 《Molecular & general genetics : MGG》1988,213(2-3):388-393
Summary We have demonstrated that precise excision of bacterial transposon Tn5 can occur in the yeast, Saccharomyces cerevisiae. Tn5 insertions in the yeast gene LYS2 were generated by transposon mutagenesis made in Escherichia coli by means of a ::Tn5 vector. Nine insertions of Tn5 into the structural part of the yeast LYS2 gene situated in a shuttle epsiomal plasmid were selected. All the plasmids with a Tn5 insertion were used to transform yeast strains carrying a deletion of the entire LYS2 gene or a deletion of the part of LYS2 overlapping the point of insertion.All insertions inactivated the LYS2 gene and were able to revert with low (about 10-8) frequencies to lysine prototrophy. Restriction analysis of revertant plasmids revealed them to be indistinguishable from the original plasmid without Tn5 insertion. DNA sequencing of the regions containing the points of insertions, made for two revertants, proved that Tn5 excision was completely precise. 相似文献
4.
The role of endogenous heparan sulfate proteoglycan in adhesion and neurite outgrowth from dorsal root ganglia 总被引:2,自引:0,他引:2
E A Chernoff 《Tissue & cell》1988,20(2):165-178
Some phases of dorsal root ganglion (DRG) substratum attachment and growth cone morphology are mediated through endogenous cell surface heparan sulfate proteoglycan. The adhesive behavior of intact embryonic chicken DRG (spinal sensory ganglia) is examined on substrata coated with fibronectin, fibronectin treated with antibody to the cell-binding site (anti-CBS), and the heparan sulfate-binding protein platelet factor four. DRG attach to fibronectin, anti-CBS-treated fibronectin, and platelet factor four. The ganglia extend an extensive halo of unfasciculated neurites on fibronectin and produce fasciculated neurite outgrowth on platelet factor four and anti-CBS antibody-treated FN. Treatment with heparinase, but not chondroitinase, abolishes adhesion to fibronectin and platelet factor four. Growth cones of DRG on fibronectin have well-spread lamellae and microspikes. On platelet factor four, and anti-CBS-treated FN, growth cones exhibit microspikes only. Isolated Schwann cells adhere equally well to fibronectin and platelet factor four, spreading more rapidly on fibronectin. Isolated DRG neurons adhere equally well on both substrata, but only 10% of the neurons extend long neurites on platelet factor four. The majority of the isolated neurons on platelet factor four exhibit persistent microspike production resembling that of the early stages of normal neurite extension. Endogenous heparan sulfate proteoglycan supports the adhesion of whole DRG, isolated DRG neurons, and Schwann cells, as well as extensive microspike activity by DRG neurons, one important part of growth cone activity. 相似文献
5.
Isolation and characterization of a large,neurite-associated glycoconjugate from neuroblastoma cells
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A high molecular weight glycoconjugate has been isolated from neurite-producing neuronal tumor cells in culture and has been designated as I(0) based on its elution characteristics in gel filtration chromatography. This molecule cannot be found in a variety of nonneuronal cells. I(0) is found in the substratum-attached material or cell fraction of neurite-producing neuroblastoma cells, depending upon culture conditions. It is found in the substratum-bound fraction of B104 rat neuroblastoma cells during serum starvation and in the EGTA-detached cell fraction of B104 cells grown in chemically defined N2 medium. It occurs only in the cell fraction of the human neuroblastoma line Platt. Examination of behavioral variants of the B104 rat line further strengthens the association of I(0) with neurite production; the constitutive neurite-producing E(R)B9 variant contains I(0) while the non-neurite-producing E(R)A11 variant does not. I(0) is large, eluting in the void volume of sepharose-CL2B columns. Radioiodination of intact cells with lactoperoxidase shows I(0) to be a cell surface component. Metabolic radiolabeling studies show that it contains a high proportion of polysaccharide to protein, does not contain mannose, and is unsulfated. Alkaline borohydride reduction release two size classes of large polysaccharide chain. The alkaline reduction results, along with the mannose incorporation studies, show the presence of O-glycosidic linkages and few, if any, N-linkages. Resistance to nitrous acid deamination, insensitivity to glycosaminoglycan lyases, and the absence of sulfation, indicate that I(0) does not contain the glycosaminoglycans hyaluronic acid, chondroitin-, dermatan-, or heparin- sulfates. Affinity column chromatography reveals high binding affinity of I(0) to polyornithine and no binding to gelatin (collagen) or the glycosaminoglycans hyaluronate and heparin. These studies describe a unique high molecular weight glycoconjugate on the surface of neurite-producing neuroblastoma cell lines from two species. 相似文献
6.
In order to examine the role of ependymal cells in the spinal cord regeneration of urodele amphibians, procedures were established to identify and culture these cells. Cell isolation and culture conditions were determined for ependymal cells from larval and adult axolotls (Ambystoma mexicanum). Dissociated cells prepared from intact spinal cords were cultured on fibronectin- or laminin-coated dishes. Dissociated cells attached more rapidly to fibronectin, but attached and spread on both fibronectin and laminin. Essentially pure populations of ependymal cells were obtained by removing 2 week old ependymal outgrowth from lesion sites of adult spinal cords. These ependymal outgrowths attached and grew only on fibronectin-coated dishes. Growth and trophic factors were tested to formulate a medium that would support ependymal cell proliferation. The necessary peptide hormones were PDGF, EGF, and insulin. TGF-beta(1) affected the organization of cell outgrowth. Initially, longterm culture required the presence of high levels of axolotl serum. Addition of purified bovine hemaglobin in the culture medium reduced the serum requirement. Outgrowth from expiants was subcultured by transferring groups of cells. Intrinsic markers were used to identify ependymal cells in culture. The ependymal cells have characteristic ring-shaped nucleoli in both intact axolotl spinal cords and in culture. Indirect immunofluorescence examination of intermediate filaments showed that ependymal cells were glial fibrillary acidic protein (GFAP) negative and vimentin positive in culture. Identification of dividing cells was made using (3)H-thymidine incorporation and autoradiography, and by the presence of mitotic figures in the cultured cells. 相似文献
7.
Deletion analysis of the SUP35 gene of the yeast Saccharomyces cerevisiae reveals two non-overlapping functional regions in the encoded protein 总被引:13,自引:0,他引:13
Michael D. Ter-Avanesyan Vitaly V. Kushnirov Adilya R. Dagkesamanskaya Svetlana A. Didichenko Yury O. Chernoff Sergey G. Inge-Vechtomov Vladimir N. Smirnov 《Molecular microbiology》1993,7(5):683-692
SUP35is an omnipotent suppressor gene of Saccharomyces cerevisiae coding for a protein consisting of a C-terminal part similar to the elongation factor EF-1α and a unique N-terminal sequence of 253 amino acids. Twelve truncated versions of the SUP35 gene were generated by the deletion of fragments internal to the coding sequence. Functional studies of these deletion mutants showed that: (i) only the EF-1α-like C-terminal part of the Sup35 protein is essential for the cell viability; (ii) overexpression of either the N-terminal part of the Sup35 protein or the full-length Sup35 protein decreases translational fidelity, resulting in omnipotent suppression and reduced growth of [psi+] strains; (iii) expression of the C-terminal part of the Sup35 protein generates an antisuppressor phenotype; and (iv) both the N- or C-terminal segments of the Sup35 protein can bind to 80S ribosomes. Thus, the data obtained define two domains within the Sup35 protein which are responsible for different functions. 相似文献
8.
Grace A. Maresh Ellen A.G. Chernoff Lloyd A. Culp 《Archives of biochemistry and biophysics》1984,233(2):428-437
Human neuroblastoma cells (Platt) were detached from tissue culture substrata with a Ca2+ chelating agent, and then the suspended cells were extracted with a sodium dodecyl sulfate (SDS)-containing buffer to maximally solubilize their sulfate-radiolabeled proteoglycans. The majority of the high-molecular-weight material in these dissociative extracts was heparan sulfate proteoglycan, which resolves into two heterodisperse size classes upon gel filtration on columns of Sepharose CL4B. After removal of SDS from these extracts by hydrophobic chromatography on Sep-Pak C18 cartridges, extracts were further fractionated on various affinity matrices. All of the sulfate-radiolabeled material eluted as one peak from DEAE-Sephadex ion-exchange columns. In contrast, affinity fractionation on Sepharose columns derivatized with the heparan sulfate-binding protein, platelet factor-4, resolved three major and one minor subsets of these components. The nonbinding fraction contained some heparan sulfate proteoglycan and some chondroitin sulfate. The weak-binding fraction contained principally heparan sulfate proteoglycan, as well as a small amount of chondroitin sulfate proteoglycan; the gel-filtration properties of these proteoglycans before or after alkaline borohydride treatment indicated that they were small in size, containing perhaps 2 to 4 glycosaminoglycan chains. The high-affinity fraction eluted from platelet factor 4-Sepharose was composed entirely of “singlechain” heparan sulfate. A portion of the heparan sulfate proteoglycan of the original extract bound to the hydrophobic affinity matrix, octyl-Sepharose, and this hydrophobic proteoglycan partitioned into the nonbinding and weak-binding fractions of the platelet factor 4-Sepharose affinity columns. These studies reveal that the majority of the proteoglycan made by these neuronal cells in culture is of the heparan sulfate class, is small in size when compared to other characterized proteoglycans, and can be resolved into several overlapping subsets when fractionated on affinity matrices. 相似文献
9.
The ecology and agronomy of Miscanthus sinensis, a species important to bioenergy crop development, in its native range in Japan: a review 总被引:1,自引:0,他引:1
J. RYAN STEWART YO TOMA† FABIÁN G. FERNÁNDEZ‡ AYA NISHIWAKI§ TOSHIHIKO YAMADA† GERMÁN BOLLERO‡ 《Global Change Biology Bioenergy》2009,1(2):126-153
Among several candidate perennial taxa, Miscanthus × giganteus has been evaluated and promoted as a promising bioenergy crop. Owing to several limitations, however, of the sterile hybrid, both at the taxon and agronomic production levels, other options need to be explored to not only improve M . × giganteus , which was originally collected in Japan, but to also consider the development of other members of its genus, including Miscanthus sinensis , as bioenergy crops. Indeed, there is likely much to be learned and applied to Miscanthus as a bioenergy crop from the long history of intensive interaction between humans and M. sinensis in Japan, which in some regions of the country spans several thousand years. Combined with its high amount of genetic variation, stress tolerance, biotic interactions with fauna, and function as a keystone species in diverse grasslands and other ecosystems within its native range, the unique and extensive management of M. sinensis in Japan as a forage grass and building material provides agronomists, agroecologists, and plant breeders with the capability of better understanding this species in terms of potential contribution to bioenergy crop development. Moreover, the studies described in this review may serve as a platform for future research of Miscanthus as a bioenergy crop in other parts of the world. 相似文献
10.
Aleksandr A Rubel Tatyana A Ryzhova Kirill S Antonets Yury O Chernoff Alexey P Galkin 《朊病毒》2013,7(6):469-476
Alzheimer disease is associated with the accumulation of oligomeric amyloid β peptide (Aβ), accompanied by synaptic dysfunction and neuronal death. Polymeric form of prion protein (PrP), PrPSc, is implicated in transmissible spongiform encephalopathies (TSEs). Recently, it was shown that the monomeric cellular form of PrP (PrPC), located on the neuron surface, binds Aβ oligomers (and possibly other β-rich conformers) via the PrP23–27 and PrP90–110 segments, acting as Aβ receptor. On the other hand, PrPSc polymers efficiently bind to Aβ monomers and accelerate their oligomerization. To identify specific PrP sequences that are essential for the interaction between PrP polymers and Aβ peptide, we have co-expressed Aβ and PrP (or its shortened derivatives), fused to different fluorophores, in the yeast cell. Our data show that the 90–110 and 28–89 regions of PrP control the binding of proteinase-resistant PrP polymers to the Aβ peptide, whereas the 23–27 segment of PrP is dispensable for this interaction. This indicates that the set of PrP fragments involved in the interaction with Aβ depends on PrP conformational state. 相似文献