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11.
The Na+-independent binding of [3H]-alanine to rat brain stem plus spinal cord was reinvestigated, in order to study in more detail the characteristics of previously described -alanine binding processes. Binding was absent when amino acid-free postnuclear supernatants or crude synaptic membranes were used. Experiments performed with several other Na+-free preparations showed a sole binding component, irrespective of the preparation used. Biochemical characterization of this Na+-independent binding, using frozen/thawed/washed synaptosomal-mitochodrial fractions, showed that binding reached a plateau between 7 min and 13 min, increasing thereafter. Binding was linear with fraction protein over a range of 200–415 g/ml incubation medium. Binding was completely inhibited by glycine, alanine, -aminobutyric acid, -aminoisobutyric acid, hypotaurine and strychnine, and to a lesser extent by 2,2-dimethyl--alanine, brucine and gelsemine. It was insensitive to taurine, -aminobutyric acid (GABA), 2-guanidinoethanesulfonic acid (GES), carnosine, and bicuculline methiodide. Binding was reversible, saturable (K
D 20 M), and heat sensitive. 相似文献
12.
A model is proposed for the effect of gramicidin A on the order and structure of phospholipid dispersions. According to this model, the addition of gramicidin A influences the surrounding lipids via two independent mechanisms. The first arises from a drop in surface pressure for those lipids substantially bounded by gramicidin A. The second mechanism arises from the increase in the phospholipid headgroup spacing due to the small polar region of the polypeptide. The model provides an explanation for the currently available NMR, X-ray diffraction and Langmuir monolayer results. The model also suggests mechanisms for the ability of gramicidin A to trigger a transition of the lipid from the lamellar to hexagonal II phase, the dependence of this transition on the lipid chain length and the formation of a lamellar phase with lysophosphatidylcholine.Abbreviations NMR
nuclear magnetic resonance
- DMPC
dimyristoylphosphatidylcholine
- S
molecular order parameter
- CSA
chemical shift anisotropy
- DPPC
dipalmitoylphosphati-dylcholine
- LPC
lysophosphatidylcholine 相似文献
13.
Summary Most of the inducible mutagenesis observed in Escherichia coli after treatment with many DNA damaging agents is dependent upon the products of the umuD,C operon. RecA-mediated proteolytic processing of UmuD yields a carboxyl-terminal fragment (UmuD) that is active for mutagenesis. Processing of UmuD is therefore a critical step in the fixation of mutations. In this paper we have analyzed the requirements for UmuD processing in vivo. Standard immuno-detection assays, coupled with a sensitive chemiluminescence detection assay, have been utilized to probe levels of chromosomally encoded Umu proteins from whole-cell E. coli extracts. We found that the derepression of additional SOS gene products, other than RecA, was not required for UmuD processing. Moreover, efficient cleavage of UmuD was observed only in the presence of elevated levels of activated RecA, suggesting that efficient processing would occur only under conditions of severe DNA damage. Detection of chromosomally encoded Umu proteins has allowed us, for the first time, to measure directly the cellular steady-state levels of these proteins under various SOS inducing conditions. UmuD was present at 180 copies per uninduced cell and was measured at 2400 copies per cell in strains that lacked a functional repressor. Induced levels of UmuC were approximately 12-fold lower than UmuD with 200 molecules per cell. These levels of cellular UmuC protein suggest that it functions through specific protein-DNA or protein-protein interactions, possibly as a lesion recognition protein or by interacting with DNA polymerase III. 相似文献
14.
Summary The distribution of two seed proteins, namely conglutin and a legumin-like globulin, in developing and mature seeds ofLupinus albus L. has been examined by immunocytochemistry and the concomitant modifications of their constituent polypeptides followed by SDS-PAGE. Both proteins were found within vacuolar protein bodies in various tissues of the cotyledons, although with some differences in the distribution patterns. The legumin-like protein was found to be deposited within the large storage parenchyma cells of the cotyledons in a manner similar to that reported for other storage proteins; little or no immunolabelling was associated with the cotyledonary epidermal and vascular parenchyma cells. In contrast conglutin was present in all cell types.A precursor of the legumin-like protein accumulated transiently in the developing cotyledon, but was subsequently modified by proteolytic cleavage. The onset of such modification was concomitant with a transition in the predominant vacuolar forms within the storage parenchyma cells. No precursor molecules of conglutin have been detected in this study, thus indicating that this protein is deposited in the protein bodies in its mature form.Abbreviations LM
light microscopy
- EM
electron microscopy
- DAF
days after flowering
- SDS-PAGE
sodium dodecyl sulphate polyacrylamide gel electrophoresis
- GAR
goat antirabbit antiserum 相似文献
15.
Stephanie J. Mihalik William J. Rhead 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,160(6):671-675
Summary The oxidation ofl-pipecolic acid to -aminoadipic acid was studied in eight species of mammals using an assay system more sensitive than those previously employed. After percoll-gradient fractionation, activity was localized to the mitochondrial-enriched fractions in tissues from rabbit, guinea pig, pig, dog, and sheep, with guinea pig kidney cortex showing greatest specific activity. These results contrast with the peroxisomal oxidation ofl-pipecolic acid observed in macaques and man (Mihalik and Rhead 1989; Mihalik et al. 1989). Rats and mice had undetectable levels of both peroxisomal and mitochondriall-pipecolic acid oxidation. In the rat, peroxisomal oxidation activity was not induced by feeding with either clofibrate or clofibrate andl-pipecolic acid. Thus, among mammals, both the ability to oxidizel-pipecolic acid and the organellar location of this oxidation is species dependent. 相似文献
16.
Summary A monoclonal mouse IgG2b antibody 19F8, directed towards a determinant on the retroviral transmembranous molecule p15E, binds selectively to certain rat tumours, including all tested yolk sac tumours, one rat colon carcinoma, one spontaneous kidney carcinoma and an adenovirus-type-9-induced rat breast tumour, as tested by antibody-dependent cellular cytotoxicity (ADCC) and immunohistochemistry. Groups of rats receiving yolk sac tumour F56 isografts intraperitoneally (i.p.) or subperitoneally (s.p.) were treated with this monoclonal antibody (mAb), 19F8, inoculated twice a week in doses of 100 µg. Parallel control groups received analogous inoculations of an isotype-matched monoclonal antibody. A significant growth inhibitory effect was observed with 19F8. In 5/10 rats isografted i.p., tumour outgrowth was completely inhibited and in the other 5 rats the outgrowth was delayed compared to the 10 rats in the control group, which all developed tumours. All rats of the control group developed large volumes of ascites, whereas the 5 rats in the therapy group with eventual tumour outgrowth had little or no ascites. In two experiments with rats carrying subperitoneal isografts and treated with the 19F8 mAb, tumour grew out in 4/5 and 5/10 rats, though growth was delayed compared to the control groups, in which 5/5 and 9/9 rats developed tumours. The tumours grew significantly more slowly in the therapy groups compared to the controls. All rats that developed tumours in the therapy groups showed an anti-idiotypic response against mAb 19F8. The single tumour-free rat in the first experiment and 1/5 tumour-free rats in the other showed no such response. The draining lymph node cells from the tumour-free animals showed a specific proliferative response to yolk sac tumour F56 cells in a mixed lymphocyte tumour cell culture (MLTC), and the MLTC-induced cells were cytotoxic to F56 but not to the natural-killer-sensitive rat T cell lymphoma G1—Tc1. The cytotoxic cell population was more than 90% CD4+. It is concluded that the two test systems for identification of the epitope of p15E detected by mAb 19F8 correlated well in detection of the epitope in the cells (immunohistochemistry) and at the cell surface (ADCC). It is also concluded that mAb 19F8 has a growth-inhibitory effect on yolk sac tumour F56 and that, as a result of the treatment, T cells with specificity for F56 are appearing in draining lymph nodes of tumour-free animals. 相似文献
17.
Hideo Ikeda 《Molecular & general genetics : MGG》1986,202(3):518-520
Summary Illegitimate recombination dependent on T4 DNA topoisomerase in a cell-free system has recently been described. In that work, recombinants between two phage DNA molecules were produced by the topoisomerase alone, without an Escherichia coli extract. In this paper, it is shown that recombination between phage and circular plasmid DNA molecules can also be detected in the presence or absence of an E. coli extract but at frequencies two or three orders of magnitude lower than that observed in the phage-phage cross. The frequency is probably lower because multiple recombination is required in the case of the phage-plasmid cross. 相似文献
18.
W. Powell P. D. S. Caligari J. S. Swanston J. L. Jinks 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,71(3):461-466
Summary Random inbred lines produced by doubled haploidy (DH) and single seed descent (SSD) have been used to investigate the genetics of -glucan (gum) content in barley (Hordeum vulgare). Genetical analyses indicated that gum content is controlled by a simple additive genetic system. Significant negative genetic correlations were observed between -glucan content, thousand grain weight and height in the DH samples. These correlations were much reduced in the SSD samples and would suggest linkage of the genes controlling these characters. The presence of repulsion linkages could be exploited in a barley breeding programme by producing F1 derived DH to generate recombinants with high thousand grain weight and low -glucan content. Genetical parameters estimated from DH and F3 samples have successfully been used to predict the number of inbred lines transgressing the parental range for -glucan content and bivariate combinations involving -glucan. 相似文献
19.
Cellulose- and xylan-degrading enzymes of Trichoderma reesei QM 9414 induced by, sophorose, xylobiose, cellulose and xylan were analyzed by isoelectric focusing. The sophorose-induced enzyme system contained two types of endo-1,4--glucanases (EC 3.2.1.4), one specific for cellulose and the other non-specific, hydrolyzing both cellulose and xylan, and exo-1,4--glucanases (cellobiohydrolases I, EC 3.2.1.91), i.e. all types of glucanases that are produced during growth on cellulose. Specific endo-1,4--xylanases (EC 3.2.1.8) present in the cellulose-containing medium were less abundant in the sophorose-induced enzyme system. Xylobiose and xylan induced only specific endo-1,4--xylanases. It is concluded that syntheses of cellulases and -xylanases in T. reesei QM 9414 are under separate control and that the non-specific endo-1,4--glucanases are constituents of the cellulose-degrading enzyme system. 相似文献
20.
D. Vakeria G. A. Codd A. M. Hawthornthwaite W. D. P. Stewart 《Archives of microbiology》1986,145(3):228-233
A gene bank of the nutritionally versatile, nitrogen-fixing cyanobacterium Chlorogloeopsis fritschii was constructed in Charon 4A. 2,800 recombinants containing 10–20 kbp C. fritschii DNA fragments were screened by Southern hybridization using probes containing the genes for the large (LSU) and small (SSU) subunits of ribulose bisphosphate carboxylase/oxygenase (RuBisCO) from Anacystis nidulans. A single recombinant plaque (CDG1) containing a 10.9 kbp EcoR1 fragment from C. fritschii hybridized to both the LSU and SSU probes, indicating a possible linkage of these RuBisCO genes in C. fritschii. RuBisCO activity and protein were detected in CDG1 lysates of Escherichia coli. Hybridization was also obtained between C. fritschii DNA and the LSU probe from Chlamydomonas reinhardtii, although no homology was detected using the LSU probe from maize or the SSU probe from pea.Abbreviations RuBisCO
d-ribulose 1,5-bisphosphate carboxylase/oxygenase
- RuBP
d-ribulose 1,5-bisphosphate
- LSU
large subunit of RuBisCO
- SSU
small subunit of RuBisCO
- SDS
sodium dodecyl sulphate
- DOC
deoxycholate 相似文献