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1.
Phytochrome A regulates red-light induction of phototropic enhancement in Arabidopsis. 总被引:20,自引:5,他引:15
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Phytochrome A (phyA) and phytochrome B photoreceptors have distinct roles in the regulation of plant growth and development. Studies using specific photomorphogenic mutants and transgenic plants overexpressing phytochrome have supported an evolving picture in which phyA and phytochrome B are responsive to continuous far-red and red light, respectively. Photomorphogenic mutants of Arabidopsis thaliana that had been selected for their inability to respond to continuous irradiance conditions were tested for their ability to carry out red-light-induced enhancement of phototropism, which is an inductive phytochrome response. We conclude that phyA is the primary photoreceptor regulating this response and provide evidence suggesting that a common regulatory domain in the phyA polypeptide functions for both high-irradiance and inductive phytochrome responses. 相似文献
2.
Over the past few years, new experimental approaches have reinforced the awareness among investigators that the heterogeneity of HDL particles indicates significant differences in production and catabolism of HDL particles. Recent kinetic studies have suggested that small HDL, containing two apolipoprotein A-I molecules per particle, are converted in a unidirectional manner to medium HDL or large HDL, containing three or four apolipoprotein A-I molecules per particle, respectively. Conversion appears to occur in close physical proximity with cells and not while HDL particles circulate in plasma. The medium and large HDL are terminal particles in HDL metabolism with large HDL, and perhaps medium HDL, being catabolized primarily by the liver. These novel kinetic studies of HDL subfraction metabolism are compelling in-vivo data that are consistent with the proposed role of HDL in reverse cholesterol transport. 相似文献
3.
Ovomucoid third domains from 100 avian species: isolation, sequences, and hypervariability of enzyme-inhibitor contact residues 总被引:12,自引:0,他引:12
M Laskowski I Kato W Ardelt J Cook A Denton M W Empie W J Kohr S J Park K Parks B L Schatzley 《Biochemistry》1987,26(1):202-221
Ovomucoids were isolated from egg whites of 100 avian species and subjected to limited proteolysis. From each an intact, connecting peptide extended third domain was isolated and purified. These were entirely sequenced by single, continuous runs in a sequencer. Of the 106 sequences we report (five polymorphisms and chicken from the preceding paper [Kato, I., Schrode, J., Kohr, W. J., & Laskowski, M., Jr. (1986) Biochemistry (preceding paper in this issue)]), 65 are unique. In all cases except ostrich (which has Ser45), the third domains are either partially or fully glycosylated at Asn45. The majority of the third domain preparations we isolated are carbohydrate-free. Alignment of the sequences shows that their structurally important residues are strongly conserved. On the other hand, those residues that are in contact with the enzyme in turkey ovomucoid third domain complex with Streptomyces griseus proteinase B [Read, R., Fujinaga, M., Sielecki, A. R., & James, M. N. G. (1983) Biochemistry 22, 4420-4433] are not conserved but instead are by far the most variable residues in the molecule. These findings suggest that ovomucoid third domains may be an exception to the widely accepted generalization that in protein evolution the functionally important residues are strongly conserved. Complete proof will require better understanding of the physiological function of ovomucoid third domains. This large set of variants differing from each other in the enzyme-inhibitor contact area and augmented by several high-resolution structure determinations is useful for the study of our sequence to reactivity (inhibitory activity) algorithm. It is also useful for the study of several other protein properties. In the connecting peptide fragment most phasianoid birds have the dipeptide Val4-Ser5, which is absent in most other orders. This dipeptide is often present in only 70-95% of the molecules and appears to arise from ambiguous excision at the 5' end of the F intron of ovomucoid. Connecting peptides from the ovomucoids of cracid birds contain the analogous Val4-Asn5 peptide. In laughing kookaburra ovomucoid third domain we found (in 91% of the molecules) Gln5A, which we interpret as arising from ambiguous intron excision at the 3' end of the F intron. 相似文献
4.
A polymerase chain reaction mediated by a single primer: cloning of genomic sequences adjacent to a serotonin receptor protein coding region. 总被引:5,自引:2,他引:3
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Under appropriate conditions, specific double-stranded DNA product was generated after amplification of genomic DNA sequences in a polymerase chain-like reaction that contained only a single primer. This type of amplification reaction was performed with a variety of primers and substrate DNAs. In addition to nonspecific heterogeneous products, 5 of 11 primers reproducibly directed synthesis of double-stranded DNA that corresponded to the region of the template that contained the authentic primer annealing site. Three of these amplified products were cloned and their ends were sequenced. All three contained a copy of the primer at both 5' ends, and the position of one of the primers represented the authentic primer binding site. In each case, the location of the second copy of the primer indicated that it had initially hybridized to a partially homologous sequence in the template DNA. This single primer reaction makes it possible to amplify and clone a DNA region of unknown sequence that is adjacent to a known DNA sequence. One of the single primer reaction products described here included sequence to the 5' side of the coding region of a serotonin receptor gene that contained a functional promoter. 相似文献
5.
6.
Design of purine nucleoside phosphorylase inhibitors 总被引:2,自引:0,他引:2
Purine nucleoside phosphorylase inhibitors hold promise as specific immunosuppressive, anti-T cell leukemic, and antiuricopoietic agents. The best inhibitors available that are biologically active have Ki values from 10(-6) to 10(-7) M and fall into two categories: noncleavable nucleosides preferably iodinated at the C-5' position and C-8-substituted guanine or acycloguanosines. More potent inhibition is shown by phosphorylated acyclonucleosides that function as multisubstrate analogs, but these compounds are excluded from cells. The X-ray analysis of the human erythrocytic enzyme is beginning to reveal the nature of the active site and to explain the structure-activity relationships that have been established with analog substrates and inhibitors. 相似文献
7.
Multiple functions for sterols in Saccharomyces cerevisiae 总被引:16,自引:0,他引:16
Analyses with a yeast sterol auxotroph indicated that there are at least four different levels of function for sterol which have been designated sparking, critical domain, domain and bulk. Growth of yeast sterol auxotrophs on cholestanol is precluded unless minute amounts of ergosterol are available. We have designated this phenomenon the sparking of growth, in which cholestanol satisfies an overall membrane sterol requirement and ergosterol fulfills a high specificity sparking function. The critical domain role for sterol is observed under conditions of lanosterol supplementation where low levels of ergosterol (10-times those necessary for sparking on cholestanol) are required for growth. The sterol functions designated domain and bulk are illustrated by assessing cellular free sterol levels and plasma membrane properties of a sterol auxotroph after growth on different concentrations of exogenously supplied sterol. Plasma membranes isolated from auxotrophs grown on domain or bulk levels of sterol underwent no lipid thermotropic transitions, while plasma membranes from cells grown on critical domain levels of sterol underwent a lipid thermotropic transition, when analyzed by steady-state fluorescence anisotropy. 相似文献
8.
Alteration of high density lipoprotein subfraction distribution with induction of serum amyloid A protein (SAA) in the nonhuman primate 总被引:1,自引:0,他引:1
Overnight chair restraint results in a dramatic increase in serum amyloid A protein (apoSAA) of nonhuman primate high density lipoprotein (HDL). To determine whether apoSAA induction resulted in a displacement of indigenous HDL protein or a change in the subfraction distribution of HDL, we analyzed the characteristics of HDL subfractions in eight vervet monkeys before and 24 hr after apoSAA induction. Blood was taken from each animal before and after chair restraint to induce apoSAA. HDL was isolated from the plasma by ultracentrifugation and agarose column chromatography. The isolated HDL was subfractionated by density gradient centrifugation and five resulting subfractions were analyzed for protein and lipid content. With apoSAA induction there was a significant increase in d less than 1.09 g/ml protein, phospholipid, and free and esterified cholesterol which resulted in a 44% increase in the total mass of this subfraction. Concomitantly, there was a significant decrease in d 1.10-1.11 g/ml protein, total cholesterol, and cholesteryl ester, which resulted in a 16% decrease in the total mass of the subfraction. The response of the d 1.10-1.11 and d greater than 1.12 g/ml subfraction protein, cholesterol, and phospholipid concentrations to chair restraint for individual animals was directly proportional to their plasma HDL concentrations. Although there was a change in the HDL subfraction concentrations after chair restraint, there was no change in the lipid composition of the HDL subfractions nor in the total amount of HDL protein. However, the apoSAA/A-I ratio was significantly increased with induction while the apoA-II + C's/A-I ratio remained unchanged. The apoSAA/A-I ratio progressively increased with the density of the HDL subfraction. The protein composition of the d greater than 1.12 g/ml subfraction was changed from an average of three apoA-I and two apoA-II (or C's) molecules per particle to an average of two apoA-I, one apoA-II (or C's), and three or four apoSAA molecules per particle after chair restraint. Thus, apoSAA was predominantly associated with the denser HDL subfractions even though the lighter HDL subfractions were the most responsive in terms of changes in concentration. These data suggest that chair restraint of nonhuman primates induces apoSAA which displaces apoA-I and apoA-II or C's from HDL without altering the overall lipid and protein composition of the particle. In addition, chair restraint alters the concentration of HDL subfractions in ways that may be independent of apoSAA induction. 相似文献
9.
10.
Distorted segregation and linkage of alcohol dehydrogenase genes in Camellia japonica L. (Theacease)
Alcohol dehydrogenase isozymes in Camellia japonica are encoded by two genes, Adh-1 and Adh-2. Both loci are expressed in seeds, and their products randomly associate into intragenic and intergenic dimers. Electrophoresis of leaf extracts reveals only the products of Adh-2. Formal genetic analysis indicated that the two Adh loci are tightly linked (combined estimate of r=0.004). Most segregations fit expected Mendelian ratios, but in some families distorted segregation was observed at Adh-1, Adh-2, or both loci. The deficient progeny class varied across families, and in two apparent backcrosses three rather than two phenotypic classes were recovered. The mechanism underlying these distortions is not known, but evidence is presented that suggests that the phenomenon is genic or segmental in nature. Plausible hypotheses include linkage of the Adh structural genes with a gametophytic self-incompatibility locus, translocation heterozygosity involving the segment bearing Adh-1 and Adh-2, or a combination of these two mechanisms. 相似文献