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951.
Horst Grunz Jochen Born Michael Davids Peter Hoppe Beate Loppnow-Blinde Lothar Tacke Heinz Tiedemann Hildegard Tiedemann 《Development genes and evolution》1989,198(1):8-13
Summary We have compared the chemical properties and biological activities of the mesoderm-inducing factor that is secreted by the Xenopus XTC cell line with the vegetalizing factor from chicken embryos. The inducing activity of the factors was tested in different concentrations on totipotent ectoderm either by implantation into early gastrulae of Triturm alpestris or by application of solutions to isolated ectoderm of early gastrulae of Xenopus laevis. Both factors have similar properties. They are not irreversibly inactivated after treatment with 6 M urea or with phenol at 60° C. Reduction with thioglycolic acid inactivates the factors completely. The inducing activity of XTC-conditioned medium decreases only slightly after treatment with 50% formic acid. The apparent molecular mass and the isoelectric point of the factors are similar. The XTC factor was partially purified by size-exclusion and reversed-phase high-pressure liquid chromatography and by isoelectric focusing. The possible relationship of these factors to transforming growth factor is discussed.Dedicated to Prof. Dr. Sulo Toivonen on the occasion of his 80th birthday 相似文献
952.
Dieter B. Wildenauer Beate Ch. Zeeb-Wälde 《Biochemical and biophysical research communications》1983,116(2):469-477
Radioactively labeled 7-azido-fluphenazine and 7-azido-triflupromazine methiodide have been synthesized and their binding to membranes of intact red blood cells and to ghosts was compared after irradiation. The results indicated that tertiary phenothiazines react with integral membrane components. We conclude from the results that amphiphilic substances solubilize in biological membranes. This is in contradiction to the proposal that these compounds are excluded from the hydrophobic core of biological membranes (Conrad & Singer (1979) Proc.Natl.Acad.Sci.U.S.A. 76, 5202-5206 and (1981) Biochemistry 20, 808-818). 相似文献
953.
Beate Rist Heike A. Wieland Klaus-Dieter Willim Annette G. Beck-Sickinger 《Journal of peptide science》1995,1(5):341-348
Four sets of centrally truncated analogues of neuropeptide Y have been synthesized. In each series the N-terminal part was constant, while the C-terminal segment was systematically varied in length. The C- and N-terminal parts were linked by 6-aminohexanoic acid. The affinity to the Y1 receptor was investigated on human neuroblastoma cells SK-N-MC. Significant differences were found between the series of peptides as well as within each set. Remarkably, the affinity did not solely depend on the length of the segment, and with increasing numbers of residues the IC50 values were not always decreased. With a given N-terminal segment, only one optimal length of the C-terminal segment was found, which suggests that it is not the amino acids themselves but their 3D arrangement and orientation that is important for high receptor affinity. 相似文献
954.
Jacques J. H. Hens Marina De Wit Frans Boomsma †‡ Marc Mercken A. Beate Oestreicher Willem Hendrik Gispen Pierre N. E. De Graan 《Journal of neurochemistry》1995,64(3):1127-1136
Abstract: B-50 (GAP-43) is a presynaptic protein kinase C (PKC) substrate implicated in the molecular mechanism of noradrenaline release. To evaluate the importance of the PKC phosphorylation site and calmodulin-binding domain of B-50 in the regulation of neurotransmitter release, we introduced two monoclonal antibodies to B-50 into streptolysin O-permeated synaptosomes isolated from rat cerebral cortex. NM2 antibodies directed to the N-terminal residues 39–43 of rat B-50 dose-dependently inhibited Ca2+ -induced radiolabeled and endogenous noradrenaline release from permeated synaptosomes. NM6 C-terminal-directed (residues 132–213) anti-B-50 antibodies were without effect in the same dose range. NM2 inhibited PKC-mediated B-50 phosphorylation at Ser41 in synaptosomal plasma membranes and permeated synaptosomes, inhibited 32 P-B-50 dephosphorylation by endogenous synaptosomal phosphatases, and inhibited the binding of calmodulin to synaptosomal B-50 in the absence of Ca2+ . Similar concentrations of NM6 did not affect B-50 phosphorylation or dephosphorylation or B-50/calmodulin binding. We conclude that the N-terminal residues 39–43 of the rat B-50 protein play an important role in the process of Ca2+ -induced noradrenaline release, presumably by serving as a local calmodulin store that is regulated in a Ca2+ - and phosphorylation-dependent fashion. 相似文献
955.
The ultrastructure of epidermal cells of tendrils of Bryonia dioica Jacq. (Cucurbitaceae) was determined using microscopic, histochemical and immunochemical techniques with focus on the tactile blep, the mechano-receptor of these cells. Tactile bleps resemble bordered pits in structure and probably in formation. They contain cytoplasm rich in endoplasmic reticulum, dictyosomes, mitochondria and microbodies. The cytoplasm is highly vesiculated and usually contains lipid-body-like structures. Cytoskeletal elements (microtubules, actin filaments) are uniquely arranged in the tactile blep, and chlorotetracycline-fluorescence analysis shows large amounts of membrane-associated calcium within the tactile blep. We propose a physically interconnected cytoskeleton-membrane device as the immediate force sensor and transducer which creates a primary intracellular signal, for which calcium is a likely candidate.Abbreviations CTC
chlorotetracycline
- ER
endoplasmic reticulum
- MT
microtubule
This work was funded by grants of the Deutsche Forschungsgemeinschaft to E.W.W. and G.W. (SFB 1462) and by the Fonds der Chemischen Industrie (literature provision). 相似文献
956.
Abstract: o-rab3 is an electric ray homologue of low molecular weight GTP-binding proteins thought to be involved in targeting of secretory vesicles to sites of exocytosis. The stimulation-dependent association of o-rab3 with synaptic vesicles was compared with that of the membrane-integral synaptic vesicle protein 2 (SV2). On application of immunoelectron microscopy and the colloidal gold technique, antibodies against either protein labeled the synaptic vesicle membrane compartment. Synaptic vesicles recycled under conditions of low frequency stimulation (0.1 Hz) retained their complement of both SV2 and o-rab3. Isolation of synaptic vesicles by density-gradient centrifugation and subsequent column chromatography yielded no indication of a stimulation-dependent release of o-rab3 from synaptic vesicles. In contrast, multivesicular bodies and vacuoles occasionally observed in the nerve terminals contained SV2 but little if any o-rab3. It is concluded that o-rab3 remains associated with the synaptic vesicle membrane compartment during stimulation-induced cycles of repeated exo- and endocytosis. o-rab3 may be lost once the vesicle enters the prelysosomal pathway. 相似文献
957.
A Tn917 mutant ofStaphylococcus carnosus TM300, nrIII, was isolated and characterized. Mutant nrIII did not take up nitrate or accumulate nitrite when grown in B-medium supplemented with up to 10 mM nitrate under anoxic conditions; however, it displayed wild-type levels of benzyl viologen-linked nitrate reductase activity. Cultivated in B-medium with nitrate under oxic conditions, mutant nrIII accumulated fivefold less nitrite than the wild-type. The mutation inS. carnosus nrIII could be complemented with a 2-kb chromosomalEcoRI-HpaI fragment from the wild-type. The gene affected by transposon insertion in mutant nrIII was cloned and sequenced. Analysis of the deduced amino acid sequence revealed that this gene, designatednarT, encodes a highly hydrophobic 42-kDa transmembrane protein of 388 amino acids and shows similarities to transport proteins that play a role in nitrate import or nitrite export. The inability of nrIII to take up nitrate under anoxic conditions and its ability to take up and accumulate nitrite in the presence of benzyl viologen, a nitrate ionophore, under the same conditions suggest that NarT represents a transport protein required for nitrate uptake under anoxic conditions inS. carnosus. 相似文献
958.
959.
Beate Rothe Bernd Rothe Peter Roggentin Roland Schauer 《Molecular & general genetics : MGG》1991,226(1-2):190-197
Summary An oligonucleotide mixture corresponding to the codons for conserved and repeated amino acid sequences of bacterial sialidases (Roggentin et al. 1989) was used to clone a 4.3 kb PstI restriction fragment of Clostridium septicum DNA in Escherichia coli. The complete nucleotide sequence of the sialidase gene was determined from this fragment. The derived amino acid sequence corresponds to a protein of 110000 Da. The ribosomal binding site and promoter-like consensus sequences were identified upstream from the putative ATG initiation codon. The molecular and immunological properties of the sialidase expressed by E. coli are similar to those of the sialidase as isolated from C. septicum. The newly synthesized protein is assumed to include a leader peptide of 26 amino acids. On sequence alignment, the sialidases from C. septicum, C. sordellii and C. perfringens show significant homologies. As in other bacterial sialidases, conserved amino acid sequences occur at four positions in the protein. Aside from the consensus sequences, only poor homology to other bacterial and viral sialidases was found. The consensus sequence could be identified even in other, non-sialidase proteins, indicating a common function or the evolutionary relatedness of these proteins. 相似文献
960.
Beate Sopott-Ehlers 《Hydrobiologia》1991,227(1):231-239
In free-living Plathelminthes, the best-known photoreceptors are pigment-cup ocelli, eyes formed of one or several pigmented supportive cells into whose cup-shaped cavity project the light-sensitive elements of one or several sensory cells. Besides these, so-called Sehkolben, photoreceptors lacking pigment granules, are found in some species. Sensory cells in plathelminth photoreceptors most commonly use microvilli as the light-sensitive organelles, but some use cilia and combinations of microvilli and cilia. Lamellate ciliary bodies with cilia whose membranes are strongly flattened and rolled and pericerebral ciliary aggregations with interwoven cilia protruding into an intracellular cavity are likely photoreceptors in that they show amplification of membrane likely to bear photoreceptive pigments. Cells with ballooned cilia and tubular vacuoles are other differentiations to which light-sensitivity has been attributed. A variety of structures serve as lenses, all usually formed from parts of the pigment cell. 相似文献