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181.
182.
Electrophysiological and biochemical responses of mouse vomeronasal receptor cells to urine-derived compounds: possible mechanism of action 总被引:1,自引:1,他引:0
Receptor cells of the vomeronasal organ (VNO) are thought to detect
pheromone-like molecules important for reproductive physiology. Several
compounds derived from male mouse urine have been demonstrated to affect
endocrine events in female mice. In the present study, the ability of these
compounds to affect VNO activity was tested. In dissociated VNO cells held
under voltage clamp conditions, application of dehydro-exo-brevicomin (DHB)
evoked an outward current at negative holding potentials and an inward
current at positive holding potentials. Under current clamp, DHB reduced
action potential firing. Since DHB application caused a decrease in
membrane conductance, this compound appeared to act by reducing inward
current through closing an ion channel. Biochemical experiments tested the
effects of DHB and 2- (sec-butyl)-4,5-dihydrothiazole (SBT) on cAMP levels
in the VNO. A mixture of DHB and SBT decreased cAMP levels in VNO sensory
tissue and had no effect on VNO non-sensory tissue. The results suggest
that pheromones have an inhibitory influence on action potential generation
and on cAMP levels in receptor cells of the VNO.
相似文献
183.
Superoxide Dismutase in Arabidopsis: An Eclectic Enzyme Family
with Disparate Regulation and Protein Localization 总被引:12,自引:1,他引:11 下载免费PDF全文
A number of environmental stresses can lead to enhanced production of superoxide within plant tissues, and plants are believed to rely on the enzyme superoxide dismutase (SOD) to detoxify this reactive oxygen species. We have identified seven cDNAs and genes for SOD in Arabidopsis. These consist of three CuZnSODs (CSD1, CSD2, and CSD3), three FeSODs (FSD1, FSD2, and FSD3), and one MnSOD (MSD1). The chromosomal location of these seven SOD genes has been established. To study this enzyme family, antibodies were generated against five proteins: CSD1, CSD2, CSD3, FSD1, and MSD1. Using these antisera and nondenaturing-polyacrylamide gel electrophoresis enzyme assays, we identified protein and activity for two CuZnSODs and for FeSOD and MnSOD in Arabidopsis rosette tissue. Additionally, subcellular fractionation studies revealed the presence of CSD2 and FeSOD protein within Arabidopsis chloroplasts. The seven SOD mRNAs and the four proteins identified were differentially regulated in response to various light regimes, ozone fumigation, and ultraviolet-B irradiation. To our knowledge, this is the first report of a large-scale analysis of the regulation of multiple SOD proteins in a plant species. 相似文献
184.
Three mutations in the Arabidopsis thaliana gene encoding the alpha subunit of tryptophan synthase were isolated by selection for resistance to 5-methylanthranilate
or 5-fluoroindole, toxic analogs of tryptophan pathway intermediates. Plants homozygous for trp3-1 and trp3-2 are light-conditional tryptophan auxotrophs, while trp3-100 is a more leaky mutant. Genetic complementation crosses demonstrated that the three mutations are allelic to each other,
and define a new complementation group. All three mutants have decreased steady-state levels of tryptophan synthase alpha
protein, and the trp3-100 polypeptide exhibits altered electrophoretic mobility. All three mutations were shown to be in the TSA1 (tryptophan synthase alpha subunit) structural gene by several criteria. Firstly, the trp3-1 mutation is linked to TSA1 on the bottom of chromosome 3. Secondly, the trp3-1 mutation was complemented when transformed with the wild-type TSA1 gene. Finally, DNA sequence analysis of the TSA1 gene revealed a single transition mutation in each trp3 mutant.
Received: 28 May 1996 / Accepted: 19 June 1996 相似文献
185.
Coordinate regulation of the tryptophan biosynthetic pathway and indolic phytoalexin accumulation in Arabidopsis. 总被引:6,自引:2,他引:4 下载免费PDF全文
Little is known about the mechanisms that couple regulation of secondary metabolic pathways to the synthesis of primary metabolic precursors. Camalexin, an indolic secondary metabolite, appears to be the major phytoalexin in Arabidopsis. It was previously shown that camalexin accumulation is caused by infection with plant pathogens, by abiotic elicitors, and in spontaneous lesions in the accelerated cell death mutant acd2. We demonstrate that the accumulation of this phytoalexin is accompanied by the induction of the mRNAs and proteins for all of the tryptophan biosynthetic enzymes tested. A strong correlation was observed between the magnitude of camalexin accumulation and the induction of tryptophan biosynthetic proteins, indicating coordinate regulation of these processes. Production of disease symptoms is not sufficient for the response because systemic infection with cauliflower mosaic virus or cucumber mosaic virus did not induce the tryptophan pathway enzymes or camalexin accumulation. Salicylic acid appears to be required, but unlike other documented pathogenesis-related proteins, it is not sufficient for the coordinate induction. Results with trp mutants suggest that the tryptophan pathway is not rate limiting for camalexin accumulation. Taken together, these results are consistent with the hypothesis that the regulation of the tryptophan pathway in plants responds to needs for biosynthesis of secondary metabolites. 相似文献
186.
Carbamoylphosphate synthetase (CPS) catalyzes the first committed step in
pyrimidine biosynthesis, arginine biosynthesis, or the urea cycle.
Organisms may contain either one generalized or two specific CPS enzymes,
and these enzymes may be heterodimeric (encoded by linked or unlinked
genes), monomeric, or part of a multifunctional protein. In order to help
elucidate the evolution of CPS, we have performed a comprehensive
phylogenetic analysis using the 21 available complete CPS sequences,
including a sequence from Sulfolobus solfataricus P2 which we report in
this paper. This is the first report of a complete CPS gene sequence from
an archaeon, and sequence analysis suggests that it encodes an enzyme
similar to heterodimeric CPSII. We confirm that internal similarity within
the synthetase domain of CPS is the result of an ancient gene duplication
that preceded the divergence of the Bacteria, Archaea, and Eukarya, and use
this internal duplication in phylogenetic tree construction to root the
tree of life. Our analysis indicates with high confidence that this
archaeal sequence is more closely related to those of Eukarya than to those
of Bacteria. In addition to this ancient duplication which created the
synthetase domain, our phylogenetic analysis reveals a complex history of
further gene duplications, fusions, and other events which have played an
integral part in the evolution of CPS.
相似文献
187.
Seegmiller A; Williams KR; Hammersmith RL; Doak TG; Witherspoon D; Messick T; Storjohann LL; Herrick G 《Molecular biology and evolution》1996,13(10):1351-1362
Internal eliminated sequences (IESs) often interrupt ciliate genes in the
silent germline nucleus but are exactly excised and eliminated from the
developing somatic nucleus from which genes are then expressed. Some long
IESs are transposons, supporting the hypothesis that short IESs are ancient
transposon relics. In light of that hypothesis and to explore the
evolutionary history of a collection of IESs, we have compared various
alleles of a particular locus (the 81 locus) of the ciliated protozoa
Oxytricha trifallax and O. fallax. Three short IESs that interrupt two
genes of the locus are found in alleles from both species, and thus must be
relatively ancient, consistent with the hypothesis that short IESs are
transposon relics. In contrast, TBE1 transposon interruptions of the locus
are allele-specific and probably the results of recent transpositions.
These IESs (and the TBE1s) are precisely excised from the DNA of the
developing somatic macronucleus. Each IES interrupts a highly conserved
sequence. A few nucleotides at the ends of each IES are also conserved,
suggesting that they interact critically with IES excision machinery.
However, most IES nucleotide positions have evolved at high rates, showing
little or no selective constraint for function. Nonetheless, the length of
each IES has been maintained (+/- 3 bp). While one IES is approximately 33
bp long, three other IESs have very similar sizes, approximately 70 bp
long. Two IESs are surrounded by direct repeats of the sequence TTCTT. No
other sequence similarities were found between any of the four IESs.
However, the ends of one IES do match the inverted terminal repeat
consensus sequence of the "TA" IESs of Paramecium. Three O. trifallax
alleles appear to have been recipients in recent conversion events that
could have been provoked by double-strand breaks associated with IES ends
subsequent to IES transposition. Our findings support the hypothesis that
short IESs evolved from ancient transposons that have lost most of their
sequences, except those necessary for precise excision during macronuclear
development.
相似文献
188.
The interglobular domain of cartilage aggrecan is cleaved by PUMP, gelatinases, and cathepsin B. 总被引:15,自引:0,他引:15
A J Fosang P J Neame K Last T E Hardingham G Murphy J A Hamilton 《The Journal of biological chemistry》1992,267(27):19470-19474
The action of three matrix metalloproteinases (MMPs), 72- and 95-kDa gelatinases (MMP-2 and MMP-9) and PUMP (MMP-7), and a cysteine proteinase, cathepsin B, were investigated on aggrecan the major proteoglycan of cartilage. All the enzymes cleaved aggrecan although the activity of the 95-kDa gelatinase was very low. Specific cleavage sites were investigated following incubation with a purified aggrecan G1-G2 domain fragment (150 kDa). Both gelatinases produced 110-kDa G2 and 56-kDa G1 products by a single cleavage at an Asn-Phe bond within the interglobular domain close to the G1 domain. This was similar to the action of stromelysin (MMP-3) (Fosang, A. J., Neame, P. J., Hardingham, T. E., Murphy, G., and Hamilton, J. A. (1991) J. Biol. Chem. 266, 15579-15582). Cathepsin B also produced two fragments from a single cleavage at a Gly-Val bond only three amino acids C-terminal to the metalloproteinase cleavage site. PUMP cleaved at the metalloproteinase Asn-Phe site, but in addition produced a low yield of a smaller G2 fragment (56 kDa) corresponding to cleavage between Asp441 and Leu442 (human sequence), within the interglobular domain, close to the G2 domain. The apparent difference in size between the two G2 fragments released by PUMP (110 and 56 kDa) was much greater than predicted from the peptide length between the cleavage sites (100 amino acids). However, keratanase digestion greatly reduced the size of the 110-kDa G2 fragment, while producing only a small reduction in size of the 56-kDa product, showing that there was approximately 30-40 kDa of keratan sulfate attached to the interglobular domain between the PUMP cleavage sites. This new structural information on aggrecan may account for the previously observed stiffness of the interglobular domains when viewed by rotary shadowing electron microscopy (Paulsson, M., Morgelin, M., Wiedemann, H., Beardmore-Gray, M., Dunham, D. G., Hardingham, T. E., Heinegard, D., Timpl, R., and Engel, J. (1987) Biochem. J. 245, 763-772). These results show that in spite of a high keratan sulfate content the interglobular domain provides important sites for cleavage by different proteinases, including several members of the matrix metalloproteinase family. 相似文献
189.
pEmu: an improved promoter for gene expression in cereal cells 总被引:5,自引:0,他引:5
D. I. Last R. I. S. Brettell D. A. Chamberlain A. M. Chaudhury P. J. Larkin E. L. Marsh W. J. Peacock E. S. Dennis 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1991,81(5):581-588
Summary A recombinant promoter, pEmu, has been constructed to give a high level of gene expression in monocots. It is based on a truncated maize Adh1 promoter, with multiple copies of the Anaerobic Responsive Element from the maize Adh1 gene and ocs-elements from the octopine synthase gene of Agrobacterium tumefaciens. The pEmu promoter was one of 12 different promoter constructs that were linked to the -glucuronidase (GUS) marker gene. Promoter activity was measured 48 h after introduction of the constructs into protoplasts of five different monocot species [wheat, maize, rice, einkorn (Triticum monococcum), and Lolium multiflorum] and one dicot (Nicotiana plumbaginifolia). In suspension cell protoplasts, the most highly expressing construct (pEmuGN) gave 10- to 50-fold higher expression than the CaMV 35S promoter in all the monocot species. The pEmu promoter should be valuable where a high level of gene expression is required in monocots. The pEmu promoter showed instability in several widely used Escherichia coli strains but was stable in a recA, recD strain AC001, which is described. Another construct, p4OCS35SIGN, gave a tenfold increase in expression over the CaMV 35S promoter in dicot (Nicotiana plumbaginifolia) protoplasts. 相似文献
190.
Serge Pieters David McGowan Florence Herschke Frederik Pauwels Bart Stoops Stefaan Last Werner Embrechts Annick Scholliers Wendy Mostmans Kris Van Dijck Bertrand Van Schoubroeck Tine Thoné Dorien De Pooter Gregory Fanning Mari Luz Rosauro Mourad Daoubi Khamlichi Ioannis Houpis Eric Arnoult Pierre Raboisson 《Bioorganic & medicinal chemistry letters》2018,28(4):711-719
The discovery of a novel series of highly potent quinazoline TLR 7/8 agonists is described. The synthesis and structure–activity relationship is presented. Structural requirements and optimization of this series toward TLR 7 selectivity afforded the potent agonist 48. Pharmacokinetic and pharmacodynamic studies highlighted 48 as an orally available endogenous interferon (IFN-α) inducer in mice. 相似文献