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1.
Hisao Tsukamoto Yoshihiro Kubo David L. Farrens Mitsumasa Koyanagi Akihisa Terakita Yuji Furutani 《The Journal of biological chemistry》2015,290(45):27176-27187
Melanopsins play a key role in non-visual photoreception in mammals. Their close phylogenetic relationship to the photopigments in invertebrate visual cells suggests they have evolved to acquire molecular characteristics that are more suited for their non-visual functions. Here we set out to identify such characteristics by comparing the molecular properties of mammalian melanopsin to those of invertebrate melanopsin and visual pigment. Our data show that the Schiff base linking the chromophore retinal to the protein is more susceptive to spontaneous cleavage in mammalian melanopsins. We also find this stability is highly diversified between mammalian species, being particularly unstable for human melanopsin. Through mutagenesis analyses, we find that this diversified stability is mainly due to parallel amino acid substitutions in extracellular regions. We propose that the different stability of the retinal attachment in melanopsins may contribute to functional tuning of non-visual photoreception in mammals. 相似文献
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4.
Some RNAs, including both single- and double-stranded RNAs, when incubated with chick embryo cell culture induce cellular resistance against viruses. Evidence was now obtained indicating that the induction of cellular resistance by RNA depends on the cellular metabolic activity, especially on the synthesis of cellular RNA and protein. Thus, inhibitors of RNA and protein synthesis, actinomycin D and cycloheximide, were found to inhibit the development of an antiviral state when added before, or during the relatively early period of, incubation of the cells with RNA. In the course of induction of cellular resistance, three stages may be distinguished, the priming stage, the developing stage, and the established resistant stage. 相似文献
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6.
In order to elucidate the evolution of C4 syndrome, the taxonomic relationships, leaf anatomy, and ecological and global distribution of C3 and C4 species in the genusRhynchospora were investigated. The anatomical observation for 181 species revealed that 26 C4 species occurred within theCapitatae group of the subgenusHaplostyleae, a natural group showing highly advanced morphological characteristics, together with several C3 species. In spite of there being rather few C4 species, they possessed two kinds of Kranz anatomical structure differing from each other in the location of Kranz cells. Some C3 species ofCapitatae showed radial arrangement in mesophyll cells surrounding vascular bundles, which is distinguished from typical non-Kranz anatomy. The C4 species extended their ecological ranges from wet habitats to dry savanna grasslands, while the C3 species showed the best development in wet habitats. The C3 species were widespread from tropical to temperate regions with partial range extension into subarctic regions of both hemispheres, showing conspicuously high concentration of species in the New World, but being absent from arid climatic regions. The C4 species were distributed mostly in tropics and subtropics, showing two separate distributional centers in South and Central America and in Tropical Asia and Australia. The range of C4 species was nearly completely included in the C3 range. In conclusion, it seems that inRhynchospora the C4 syndrome evolved relatively recently, and arose in at least two separate phylogenetic trends in the tropics and the subtropics, more probably in the Neotropics. 相似文献
7.
Thymidylate synthetase (EC 2.1.1.45) from rat regenerating liver has been purified over 5000-fold to apparent homogeneity by a procedure involving two affinity methods. Molecular weight of the native enzyme was found to be about 68,000, as determined by gel filtration. Electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate yielded a single band of molecular weight of 35,000, suggesting that thymidylate synthetase is a dimer of very similar or identical subunits. The Michaelis constants for deoxyuridylate (dUMP) and (+/-)L-5,10-methylenetetrahydrofolate are 6.8 microM and 65 microM, respectively. Reaction kinetics and product inhibition studies reveal the enzymatic mechanism to be ordered sequential. 5-Fluoro-dUMP, halogenated analog of the nucleotide substrate is a competitive inhibitor of the enzyme, with an apparent Ki value of 5 nM. Amethopterin, analog of the cofactor is also a competitive inhibitor with an apparent Ki value of 23 microM. 相似文献
8.
Aminergic and peptidergic amplification of intracellular cyclic AMP levels in a molluscan neural network 总被引:1,自引:0,他引:1
1. Serotonin (5-hydroxytryptamine; 5-HT), dopamine (DA), and small cardioactive peptide B (SCPB) can activate adenylate cyclase and increase the intracellular cyclic AMP (cAMP) levels in the Limax procerebrum (PC), with differing time courses and to differing extents. 5-HT and SCPB are potent stimulators of adenylate cyclase, and when both were applied simultaneously, an additive effect was observed. 2. In contrast, DA shows a great variability in the time course of cAMP synthesis and is a weak stimulator. Ergonovine, a DA antagonist, failed to inhibit cyclase activation, indicating that ergonovine-sensitive receptors are absent or ergonovine-sensitive DA receptors are not coupled to adenylate cyclase. 3. 5-HT and SCPB cause a rapid synthesis of cAMP, reaching the maximum 20- to 30-fold increase within a minute. DA's effect is slow in onset and very prolonged, reaching a maximum of only a two- to three-fold increase in the cAMP level. Reasons for variability in DA action are discussed. 相似文献
9.
Heinz W. Kunz Andrea L. Cortese Hassett Tetsuo Inomata D. N. Misra Thomas J. Gill III 《Immunogenetics》1989,30(3):181-187
A new antigenic system in the rat homologous to theQa/TL antigen system in the mouse has been characterized. It was detected by antibodies raised in donor-recipient combinations
that were matched for theRT1. A, B, D, E loci in the major histocompatibility complex (MHC): (R11×BN)F1 anti-BN.1L(LEW), (R18×BN)F1 anti-BN.1L, and BN.1LV1(F344) anti-BN.1L. Absorption analyses using these antisera and a variety of inbred, congenic and
recombinant strains identified three alleles,RT1.G
a
,G
b
,G
c
, of whichG
c
is a null allele. The strain distribution of these alleles was determined, using 37 strains of rats representative of all
of the prototypic haplotypes and a number of congenic and recombinant strains. The use of the congenic and recombinant strains
showed that theRT1.G locus was linked to the MHC and that the most probable gene order wasA-E-G. Testcross analysis showed that the map distance betweenA andG was 1.4 cM(4/285 recombinants). The RT1.G antigen has a heavy chain ofM
r 46 000 and is present on both T and B cells. 相似文献
10.
The increases in the activities of hepatic thymidylate synthetase and thymidine kinase were significantly suppressed at 24 h after 70% partial hepatectomy in rats which had been administered a microtubule disrupter, colchicine or vincristine. The decrease of these enzymic activities was accompanied by a reduction of DNA content in 24 h regenerating liver. The immunoblotting assay showed that the depression of the thymidylate synthetase activity by the injection of colchicine or vincristine was due to the decrease of the enzyme protein. These results indicate that colchicine and vincristine inhibit the DNA synthesis during liver regeneration by inhibiting the induction of the key enzyme in DNA synthesis. 相似文献