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351.
Characterization of a multifunctional methyltransferase from the orchid <Emphasis Type="Italic">Vanilla planifolia</Emphasis> 总被引:2,自引:0,他引:2
The final enzymatic step in the synthesis of the flavor compound vanillin (4-hydroxy-3-methoxybenzaldehyde) is believed to be methylation of 3,4-dihydroxybenzaldehyde. We have isolated and functionally characterized a cDNA that encodes a multifunctional methyltransferase from Vanilla planifolia tissue cultures that can catalyze the conversion of 3,4-dihydroxybenzaldehyde to vanillin, although 3,4-dihydroxybenzaldehyde is not the preferred substrate. The higher catalytic efficiency of the purified recombinant enzyme with the substrates caffeoyl aldehyde and 5-OH-coniferaldehyde, and its tissue distribution, suggest this methyltransferase may primarily function in lignin biosynthesis. However, since the enzyme characterized here does have 3,4-dihydroxybenzaldehyde-O-methyltransferase activity, it may be useful in engineering strategies for the synthesis of natural vanillin from alternate sources.Abbreviations COMT Caffeic acid O-methyltransferase - DOMT 3,4-Dihydroxybenzaldehyde-O-methyltransferase - OMTs O-Methyltransferases - SAM S-adenosyl-l-methionine 相似文献
352.
353.
Zambacos GJ Nguyen D Morris RJ 《Plastic and reconstructive surgery》2004,114(3):706-10; discussion 711-2
Irrigation of breast implants and breast implant pockets with various solutions, including povidone iodine, has been a common practice among plastic surgeons for many years. Recent reports of potential weakening of silicone tubing have led the Food and Drug Administration to pronounce any contact of povidone iodine with breast implants a contraindication. An in vitro experimental study was undertaken to assess the effect of povidone iodine on the physical properties of silicone breast implant shells. Identical specimens were obtained from the shells of silicone breast implants according to published standards. The specimens were randomly assigned to eight groups of five and incubated in various solutions of decreasing concentration of povidone iodine (10% to 0.01%), and a control group (0.9% saline) was used. The containers were stored in a warming cabinet at 37 degrees C for 4 weeks. Testing of the specimens for tensile strength following 4 weeks of incubation showed no significant difference among any of the groups, including the control group. In addition, no correlation was shown between the concentration of the solution used and the tensile strength of the specimens. 相似文献
354.
355.
Genome shuffling improves degradation of the anthropogenic pesticide pentachlorophenol by Sphingobium chlorophenolicum ATCC 39723 总被引:4,自引:0,他引:4
Pentachlorophenol (PCP), a highly toxic anthropogenic pesticide, can be mineralized by Sphingobium chlorophenolicum, a gram-negative bacterium isolated from PCP-contaminated soil. However, degradation of PCP is slow and S. chlorophenolicum cannot tolerate high levels of PCP. We have used genome shuffling to improve the degradation of PCP by S. chlorophenolicum. We have obtained several strains that degrade PCP faster and tolerate higher levels of PCP than the wild-type strain. Several strains obtained after the third round of shuffling can grow on one-quarter-strength tryptic soy broth plates containing 6 to 8 mM PCP, while the original strain cannot grow in the presence of PCP at concentrations higher than 0.6 mM. Some of the mutants are able to completely degrade 3 mM PCP in one-quarter-strength tryptic soy broth, whereas no degradation can be achieved by the wild-type strain. Analysis of several improved strains suggests that the improved phenotypes are due to various combinations of mutations leading to an enhanced growth rate, constitutive expression of the PCP degradation genes, and enhanced resistance to the toxicity of PCP and its metabolites. 相似文献
356.
Chen L Xie L Dai Y Xiong X Fan W Zhang R 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2004,139(4):669-679
Nacre formation is an ideal model to study biomineralization processes. Although much has been done about biomineralization mechanism of nacre, little is known as to how cellular signaling regulates this process. We are interested in whether G protein signaling plays a role in mineralization. Degenerate primers against conserved amino acid regions of G proteins were employed to amplify cDNA from the pearl oyster Pinctada fucata. As a result, the cDNA encoding a novel G(s)alpha (pfG(s)alpha) from the pearl oyster was isolated. The G(s)alpha cDNA encodes a polypeptide of 377 amino acid residues, which shares high similarity to the octopus (Octopus vulgaris) G(s)alpha. The well-conserved A, C, G (switch I), switch II functional domains and the carboxyl terminus that is a critical site for interaction with receptors are completely identical to those from other mollusks. However, pfG(s)alpha has a unique amino acid sequence, which encodes switch III and interaction sites of adenylyl cyclase respectively. In situ hybridization and Northern blotting analysis revealed that the oyster G(s)alpha mRNA is widely expressed in a variety of tissues, with highest levels in the outer fold of mantle and epithelia of gill, the regions essential for biomineralization. We also show that overexpression of the pfG(s)alpha in mammalian MC3T3-E1 cells resulted in increased cAMP levels. Mutant pfG(s)alpha that has impaired CTX substrate diminished its ability to induce cAMP production. Furthermore, the alkaline phosphatase (ALP) activity, an indicator for mineralization, is induced by the G(s)alpha in MC3T3-E1 cells. These results indicated that G(s)alpha may be involved in regulation of physiological function, particularly in biological biomineralization. 相似文献
357.
358.
Yu YY Chen Y Dai G Chen J Sun XM Wen CJ Zhao DH Chang DC Li CJ 《The international journal of biochemistry & cell biology》2004,36(8):1562-1572
Calmodulin is a major cytoplasmic calcium receptor that performs multiple functions in the cell including cytokinesis. Central spindle appears between separating chromatin masses after metaphase-anaphase transition. The interaction of microtubules from central spindle with cell cortex regulates the cleavage furrow formation. In this paper, we use green fluorescence protein (GFP)-tagged calmodulin as a living cell probe to examine the detailed dynamic redistribution and co-localization of calmodulin with central spindle during cytokinesis and the function of this distribution pattern in a tripolar HeLa cell model. We found that calmodulin is associated with spindle microtubules during mitosis and begins to aggregate with central spindle after anaphase initiation. The absence of either central spindle or central spindle-distributed calmodulin is correlated with the defect in the formation of cleavage furrow, where contractile ring-distributed CaM is also extinct. Further analysis found that both the assembly of central spindle and the formation of cleavage furrow are affected by the W7 treatment. The microtubule density of central spindle was decreased after the treatment. Only less than 10% of the synchronized cells enter cytokinesis when treated with 25 microM W7, and the completion time of furrow regression is also delayed from 10 min to at least 40 min. It is suggested that calmodulin plays a significant role in cytokinesis including furrow formation and regression, The understanding of the interaction between calmodulin and microtubules may give us insight into the mechanism through which calmodulin regulates cytokinesis. 相似文献
359.
Dai H Shin OH Machius M Tomchick DR Südhof TC Rizo J 《Nature structural & molecular biology》2004,11(9):844-849
The neuronal protein synaptotagmin 1 functions as a Ca(2+) sensor in exocytosis via two Ca(2+)-binding C(2) domains. The very similar synaptotagmin 4, which includes all the predicted Ca(2+)-binding residues in the C(2)B domain but not in the C(2)A domain, is also thought to function as a neuronal Ca(2+) sensor. Here we show that, unexpectedly, both C(2) domains of fly synaptotagmin 4 exhibit Ca(2+)-dependent phospholipid binding, whereas neither C(2) domain of rat synaptotagmin 4 binds Ca(2+) or phospholipids efficiently. Crystallography reveals that changes in the orientations of critical Ca(2+) ligands, and perhaps their flexibility, render the rat synaptotagmin 4 C(2)B domain unable to form full Ca(2+)-binding sites. These results indicate that synaptotagmin 4 is a Ca(2+) sensor in the fly but not in the rat, that the Ca(2+)-binding properties of C(2) domains cannot be reliably predicted from sequence analyses, and that proteins clearly identified as orthologs may nevertheless have markedly different functional properties. 相似文献
360.
Kniazeff J Bessis AS Maurel D Ansanay H Prézeau L Pin JP 《Nature structural & molecular biology》2004,11(8):706-713
Membrane receptors, key components in signal transduction, often function as dimers. These include some G protein-coupled receptors such as metabotropic glutamate (mGlu) receptors that have large extracellular domains (ECDs) where agonists bind. How agonist binding in dimeric ECDs activates the effector domains remains largely unknown. The structure of the dimeric ECDs of mGlu(1) solved in the presence of agonist revealed two specific conformations in which either one or both protomers are in an agonist-stabilized closed form. Here we examined whether both conformations correspond to an active form of the full-length receptor. Using a system that allows the formation of dimers made of a wild-type and a mutant subunit, we show that the closure of one ECD per dimer is sufficient to activate the receptor, but the closure of both ECDs is required for full activity. 相似文献