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91.
Summary The putative second messenger of certain atrial natriuretic factor (ANF) signal transductions is cyclic GMP. Recently, we purified a 180-kDa protein, apparently containing both ANF receptor and guanylate cyclase activities, and hypothesized that this is one of the cyclic GMP transmembrane signal transducers. The enzyme is ubiquitous and appears to be conserved. Utilizing the 180-kDa membrane guanylate cyclase, we now show that the 180-kDa guanylate cyclase is regulated in opposing fashions by two receptor signals—ANF stimulating it and protein kinase C inhibiting it. Furthermore, protein kinase C phosphorylates the 180-kDa enzyme. This suggests a novel switch on and switch off mechanism of the cyclic GMP signal transduction. Switch off represents the phosphorylation while switch on the dephosphorylation of the enzyme. 相似文献
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93.
V. I. Duda A. V. Lebedinsky M. S. Mushegjan L. L. Mitjushina 《Archives of microbiology》1987,148(2):121-127
An obligately anaerobic sporeforming bacterium assigned to a new genus and species Anaerobacter polyendosporus gen. et spec. nov. is described. Characteristic features distinguishing the bacterium from known anaerobic sporeformers were variable cell shape, including spherical, the ability to form up to five endospores per cell, diffusive distribution of reserve polysaccharide throughout the cytoplasm, independence from growth factors. The eubacterial nature of the organism was revealed by its sensitivity to 1 mg/l of streptomycin, rifampicin, penicillin and to lysozyme. It belonged to Firmicutes by the type of cell wall structure. The cell wall consisted of one layer; the outer membrane was absent. The cells were not motile. The spores were spherical or oval, heat-resistant, contained dipicolinic acid and had typical endospore structure. Cortex, coats, spore coare, and in most cases exosporium could be distinguished. The bacterium fermented carbohydrates, but not amino acids. The products of fermentation included ethanol, acetate, lactate, butyrate, butanol, H2 and CO2. Sulfate or nitrate could not be used as electron acceptors, but nitrite was reduced to NH
4
+
in a dissimilatory process. The bacterium was capable of fixing N2. The G + C content of the DNA was 29 mol %. The bacterium was isolated from meadow-gley soil. 相似文献
94.
Positive and negative control of nod gene expression in Rhizobium meliloti is required for optimal nodulation 总被引:17,自引:0,他引:17 下载免费PDF全文
Kondorosi E Gyuris J Schmidt J John M Duda E Hoffmann B Schell J Kondorosi A 《The EMBO journal》1989,8(5):1331-1340
We show that expression of common nodulation genes in Rhizobium meliloti is under positive as well as negative control. A repressor protein was found to be involved in the negative control of nod gene expression. Whereas the activator NodD protein binds to the conserved cis-regulatory element (nod-box) required for coordinated regulation of nod genes, the repressor binds to the overlapping nodD1 and nodA promoters, at the RNA polymerase binding site. A model depicting the possible interaction of the plant-derived nod gene inducer (luteolin), the NodD and the repressor with the nod promoter elements is presented. Mutants lacking the repressor exhibited delayed nodulation phenotype, indicating that fine tuning of nod gene expression is required for optimal nodulation of the plant host. 相似文献
95.
Studies on histomorphometrical changes in different segments (infundibulum, magnum, isthmus, shell gland and vagina) of oviduct of mallard, Anas platyrhynchos during active and quiescent phases of the reproductive cycle have been made. The absolute and per cent length and width of each segment showed a marked change. The magnum showed an increase of 280 per cent. Of all the histological parameters studied the number and height of mucosal folds and mucosal epithelium showed more marked increase in all segments of oviduct. The size of tubular glands and frequency of ciliated and secretory cells were studied in relation to oviductal activity. 相似文献
96.
A fraction of polar lipids was isolated from spores of the anaerobic bacterium Clostridium butyricum 35/11 exerting a noticeable radioprotective effect. The main biological activity of spore extracts was associated with this fraction. The fraction of polar lipids inhibited autolysis of the bacterial cell walls. The fraction was found to contain a phenolic glycolipid and a peptide component. The bacteriostatic and radiotherapeutic properties of the fraction are presumed to be due to its membranotropic activity. 相似文献
97.
In bacteriophage λ, the overlapping open reading frames G and T are expressed by a programmed translational frameshift similar to that of the gag-pol genes of many retroviruses to produce the proteins gpG and gpGT. An analogous frameshift is widely conserved among other dsDNA tailed phages in their corresponding “G” and “GT” tail genes even in the absence of detectable sequence homology. The longer protein gpGT is known to be essential for tail assembly, but the requirement for the shorter gpG remained unclear because mutations in gene G affect both proteins. A plasmid system that can direct the efficient synthesis of tails was created and used to show that gpG and gpGT are both essential for correct tail assembly. Phage complementation assays under conditions where levels of plasmid-expressed gpG or gpGT could be altered independently revealed that the correct molar ratio of these two related proteins, normally determined by the efficiency of the frameshift, is also crucial for efficient assembly of functional tails. Finally, the physical connection between the G and T domains of gpGT, a consequence of the frameshift mechanism of protein expression, appears to be important for efficient tail assembly. 相似文献
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100.
The effect of stimulation of the anterior lobe (AL) of the cerebellum on spinobulbo-spinal (SBS) reflex activity evoked by somatic and splanchnic afferentation was studied in chloralose-anaesthetized cats. Unit activity synchronous with the SBS component of the efferent discharge was observed at the level of motoneurons, descending axons of the dorsolateral and ventral funiculi and neurones of the reticular formation (RF). Conditioning stimulation of the AL inhibited this unit activity. Reticular formation units influenced from the AL had direct contact with segmental structures; these results showed that disappearance of the SBS reflex during AL conditioning is associated with the depressant effect of the cerebellar cortex on the reticular formation. 相似文献