Screening of Korean forest plants for rat lens aldose reductase inhibition.
(1/1498)
Naturally occurring substances which can prevent and treat diabetic complications were sought by examining ethanol extracts prepared from Korean forest plants for their inhibitory effects on rat lens aldose reductase activity in vitro. Among the plants examined, Acer ginnala, Illicium religiosum and Cornus macrophylla exerted the most strong inhibitory activity on aldose reductase. (+info)
Antioxidative and chelating activities of phenylpropanoid glycosides from Pedicularis striata.
(2/1498)
AIM: To study the antioxidative and iron chelating activities of phenylpropanoid glycosides (PPG) isolated from a Chinese herb Pedicularis striata. METHODS: Antioxidative effects of PPG on lipid peroxidation induced by FeSO4-edetic acid in linoleic acid were measured by thiobarbituric acid method. Chelating activities of PPG for Fe2+ were tested by differential spectrum method. RESULTS: The reaction rates (A532.min-1) of lipid peroxidation were 0.0046 in the control, 0.0021 in verbascoside group, and 0.0008 in isoverbascoside group. The chelating activity of isoverbascoside was 2-fold stronger than that of verbascoside. Permethyl verbascoside showed neither antioxidative nor chelating activities. CONCLUSION: The inhibitory effects of PPG with phenolic hydroxy groups on lipid peroxidation are owing to their chelating properties. Under physiological condition PPG-Fe2+ chelates are sufficiently stable. Thus PPG are able to inhibit the Fe(2+)-dependent lipid peroxidation in vivo through chelating Fe2+ and exhibit their therapeutic potential by the same mechanism in vitro. (+info)
Continuous primary sequence requirements in the 18-nucleotide promoter of dicot plant mitochondria.
(3/1498)
The nucleotide requirements of mitochondrial promoters of dicot plants were studied in detail in a pea in vitro transcription system. Deletions in the 5' regions of three different transcription initiation sites from pea, soybean, and Oenothera identified a crucial AT-rich sequence element (AT-Box) comprising nucleotide positions -14 to -9 relative to the first transcribed nucleotide. Transversion of the AT-Box sequence to comple- mentary nucleotide identities results in an almost complete loss of promoter activity, suggesting that primary structure rather than a simple accumulation of adenines and thymidines in this region is essential for promoter activity. This promoter segment thus appears to be involved in sequence specific binding of a respective protein factor(s) rather than merely loosening and melting the DNA helix during or for an initiation event. Manipulation of nucleotide identities in the 3' portion of the pea atp9 promoter and the respective 3'-flanking region revealed that essential sequences extend to positions +3/+4 beyond this transcription start site. Efficient transcription initiation at an 18-base pair promoter sequence ranging from nucleotide positions -14 to +4 integrated into different sequence contexts shows this element to be sufficient for autonomous promoter function independent of surrounding sequences. (+info)
Characterization of two novel type I ribosome-inactivating proteins from the storage roots of the andean crop Mirabilis expansa.
(4/1498)
Two novel type I ribosome-inactivating proteins (RIPs) were found in the storage roots of Mirabilis expansa, an underutilized Andean root crop. The two RIPs, named ME1 and ME2, were purified to homogeneity by ammonium sulfate precipitation, cation-exchange perfusion chromatography, and C4 reverse-phase chromatography. The two proteins were found to be similar in size (27 and 27.5 kD) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and their isoelectric points were determined to be greater than pH 10.0. Amino acid N-terminal sequencing revealed that both ME1 and ME2 had conserved residues characteristic of RIPs. Amino acid composition and western-blot analysis further suggested a structural similarity between ME1 and ME2. ME2 showed high similarity to the Mirabilis jalapa antiviral protein, a type I RIP. Depurination of yeast 26S rRNA by ME1 and ME2 demonstrated their ribosome-inactivating activity. Because these two proteins were isolated from roots, their antimicrobial activity was tested against root-rot microorganisms, among others. ME1 and ME2 were active against several fungi, including Pythium irregulare, Fusarium oxysporum solani, Alternaria solani, Trichoderma reesei, and Trichoderma harzianum, and an additive antifungal effect of ME1 and ME2 was observed. Antibacterial activity of both ME1 and ME2 was observed against Pseudomonas syringae, Agrobacterium tumefaciens, Agrobacterium radiobacter, and others. (+info)
The prenylation status of a novel plant calmodulin directs plasma membrane or nuclear localization of the protein.
(5/1498)
Post-translational attachment of isoprenyl groups to conserved cysteine residues at the C-terminus of a number of regulatory proteins is important for their function and subcellular localization. We have identified a novel calmodulin, CaM53, with an extended C-terminal basic domain and a CTIL CaaX-box motif which are required for efficient prenylation of the protein in vitro and in vivo. Ectopic expression of wild-type CaM53 or a non-prenylated mutant protein in plants causes distinct morphological changes. Prenylated CaM53 associates with the plasma membrane, but the non-prenylated mutant protein localizes to the nucleus, indicating a dual role for the C-terminal domain. The subcellular localization of CaM53 can be altered by a block in isoprenoid biosynthesis or sugar depletion, suggesting that CaM53 activates different targets in response to metabolic changes. Thus, prenylation of CaM53 appears to be a novel mechanism by which plant cells can coordinate Ca2+ signaling with changes in metabolic activities. (+info)
Tissue-specific expression of the beta-subunit of tryptophan synthase in Camptotheca acuminata, an indole alkaloid-producing plant.
(6/1498)
Camptothecin is an anticancer drug produced by the monoterpene indole alkaloid pathway in Camptotheca acuminata. As part of an investigation of the camptothecin biosynthetic pathway, we have cloned and characterized a gene from C. acuminata encoding the beta-subunit of tryptophan (Trp) synthase (TSB). In C. acuminata TSB provides Trp for both protein synthesis and indole alkaloid production and therefore represents a junction between primary and secondary metabolism. TSB mRNA and protein were detected in all C. acuminata organs examined, and their abundance paralleled that of camptothecin. Within each shoot organ, TSB was most abundant in vascular tissues. Within the root, however, TSB expression was most abundant in the outer cortex. TSB has been localized to chloroplasts in Arabidopsis, but there was little expression of TSB in C. acuminata tissues where the predominant plastids were photosynthetically competent chloroplasts. Expression of the promoter from the C. acuminata TSB gene in transgenic tobacco plants paralleled expression of the native gene in C. acuminata in all organs except roots. TSB is also highly expressed in C. acuminata during early seedling development at a stage corresponding to peak accumulation of camptothecin, consistent with the idea that Trp biosynthesis and the secondary indole alkaloid pathway are coordinately regulated. (+info)
Expression of 1-aminocyclopropane-1-carboxylate oxidase during leaf ontogeny in white clover.
(7/1498)
We examined the expression of three distinct 1-aminocyclopropane-1-carboxylic acid oxidase genes during leaf ontogeny in white clover (Trifolium repens). Significant production of ethylene occurs at the apex, in newly initiated leaves, and in senescent leaf tissue. We used a combination of reverse transcriptase-polymerase chain reaction and 3'-rapid amplification of cDNA ends to identify three distinct DNA sequences designated TRACO1, TRACO2, and TRACO3, each with homology to 1-aminocyclopropane-1-carboxylic acid oxidase. Southern analysis confirmed that these sequences represent three distinct genes. Northern analysis revealed that TRACO1 is expressed specifically in the apex and TRACO2 is expressed in the apex and in developing and mature green leaves, with maximum expression in developing leaf tissue. The third gene, TRACO3, is expressed in senescent leaf tissue. Antibodies were raised to each gene product expressed in Escherichia coli, and western analysis showed that the TRACO1 antibody recognizes a protein of approximately 205 kD (as determined by gradient sodium dodecyl sulfate-polyacylamide gel electrophoresis) that is expressed preferentially in apical tissue. The TRACO2 antibody recognizes a protein of approximately 36.4 kD (as determined by gradient sodium dodecyl sulfate-polyacylamide gel electrophoresis) that is expressed in the apex and in developing and mature green leaves, with maximum expression in mature green tissue. No protein recognition by the TRACO3 antibody could be detected in senescent tissue or at any other stage of leaf development. (+info)
Evolution of the mitochondrial rps3 intron in perennial and annual angiosperms and homology to nad5 intron 1.
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The plant mitochondrial rps3 intron was analyzed for substitution and indel rate variation among 15 monocot and dicot angiosperms from 10 genera, including perennial and annual taxa. Overall, the intron sequence was very conserved among angiosperms. Based on length polymorphism, 10 different alleles were identified among the 10 genera. These allelic differences were mainly attributable to large indels. An insertion of 133 nucleotides, observed in the Alnus intron was partially or completely absent in the other lineages of the family Betulaceae. This insertion was located within domain IV of the secondary-structure model of this group IIA intron. A mobile element of 47 nucleotides that showed homology to sequences located in rice rps3 intron and in intergenic plant mitochondrial genomes was found within this insertion. Both substitution and indel rates were low among the Betulaceae sequences, but substitution rates were increasingly larger than indel rates in comparisons involving more distantly related taxa. From a secondary-structure model, regions involved in helical structures were shown to be well preserved from indels as compared to substitutions, but compensatory changes were not observed among the angiosperm sequences analyzed. Using approximate divergence times based on the fossil record, substitution and indel rate heterogeneity was observed between different pairs of annual and perennial taxa. In particular, the annual petunia and primrose evolved more than 15 and 10 times faster, for substitution and indel rates respectively, than the perennial birch and alder. This is the first demonstration of an evolutionary rate difference between perennial and annual forms in noncoding DNA, lending support to neutral causes such as the generation time, population size, and speciation rate effects to explain such rate heterogeneity. Surprisingly, the sequence from the rps3 intron had a high identity with the sequence of intron 1 from the angiosperm mitochondrial nad5 gene, suggesting a common origin of these two group IIA introns. (+info)