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1.
Recent studies have revealed an unexpected synergism between two seemingly unrelated protein families: CCN matricellular proteins
and the tumor necrosis factor (TNF) family of cytokines. CCN proteins are dynamically expressed at sites of injury repair
and inflammation, where TNF cytokines are also expressed. Although TNFα is an apoptotic inducer in some cancer cells, it activates
NFκB to promote survival and proliferation in normal cells, and its cytotoxicity requires inhibition of de novo protein synthesis
or NFκB signaling. The presence of CCN1, CCN2, or CCN3 overrides this requirement and unmasks the apoptotic potential of TNFα,
thus converting TNFα from a proliferation-promoting protein into an apoptotic inducer. These CCN proteins also enhance the
cytotoxicity of other TNF cytokines, including LTα, FasL, and TRAIL. Mechanistically, CCNs function through integrin α6β1 and the heparan sulfate proteoglycan (HSPG) syndecan-4 to induce reactive oxygen species (ROS) accumulation, which is essential
for apoptotic synergism. Mutant CCN1 proteins defective for binding α6β1-HSPGs are unable to induce ROS or apoptotic synergism with TNF cytokines. Further, knockin mice that express an α6β1-HSPG-binding defective CCN1 are blunted in TNFα- and Fas-mediated apoptosis, indicating that CCN1 is a physiologic regulator
of these processes. These findings implicate CCN proteins as contextual regulators of the inflammatory response by dictating
or enhancing the cytotoxicity of TNFα and related cytokines. 相似文献
2.
A simple and rapid method is described for the purification of supercoiled PM2 DNA by affinity chromatography on columns of H1 histone covalently coupled to agarose. The method does not require the use of intercalating agents or ultracentrifugation procedures. Under the conditions most appropriate for purification, elution is carried out in a single step with buffered 0.7 M NaCl after the sample has been loaded onto the column in buffered 0.2 M NaCl. The DNA eluted at the higher salt concentration consists of supercoiled closed circular DNA at greater than 90% purity independently of the ratio of supercoiled to nicked circular DNA in the input mixture. 相似文献
3.
Dissection of the effector-binding site and complementation studies of Escherichia coli phosphofructokinase using site-directed mutagenesis 总被引:1,自引:0,他引:1
A systematic study by site-directed mutagenesis has been conducted on the effector site of phosphofructokinase from Escherichia coli to delineate the role of side chains in binding the allosteric activator, GDP, and inhibitor, PEP, and to search for key residues in the allosteric transtion. Target residues were identified from the crystal structure of the enzyme-nucleoside diphosphate complex. It is found that both activator and inhibitor bind to the same set of amino acid side chains. Deletion of positively charged groups (Arg21, Arg25, Arg54, Arg154, and Lys213 mutated to alanine) weakens binding of both effectors by 2-3 kcal/mol, consistent with the disruption of charged hydrogen bonds. Residue Glu187, which is known from the crystal structure to bind the coordinated Mg2+ ion of GDP, is found to have a unique behavior on mutation and appears to be crucial in triggering the allosteric transition. All other residues mutated simply weaken binding of both PEP and GDP in a parallel manner. However, mutation of Glu----Ala187 reverses the roles of GDP and PEP, causing GDP to become an allosteric inhibitor and PEP an activator. Mutation of Glu----Gln187 has only a small effect on the binding of PEP, and both PEP and GDP are inhibitors. Studies are described in which mutations in different subunits of a tetrameric complex complement each other. The effector site is composed of residues from two subunits. In particular, Arg21 and Lys213 in each site are from different subunits. Mutations of either one of these residues abolishes activation by GDP of the homotetramer.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
PYCNOGENOL is an antioxidant phytochemical shown to have antiinflammatory activity in both the in vitro and in vivo models. This study compared the effects of chewing gums with and without PYCNOGENOL on gingival bleeding and plaque formation in 40 human subjects. In this double-blind study, subjects were assigned randomly to receive either control gums without PYCNOGENOL or experimental gums containng 5 mg PYCNOGENOL. Subjects used chewing gums for 14 days. Gingival bleeding and plaque scores were taken before and after the experiment. PYCNOGENOL chewing gums significantly reduced gingival bleeding, while no changes were noted in bleeding indexes in control subjects who used regular chewing gums. Subjects using regular control gums had significant increases of dental plaque accumulation during the two-week period. No increases in plaque accumulation were noted in subjects using PYCNOGENOL chewing gums. The data of this study suggest that the use of Pycnogenol chewing gums can minimize gingival bleeding and plaque accumulation. 相似文献
5.
G Prefontaine P Fast P C Lau M A Hefford Z Hanna R Brousseau 《Applied and environmental microbiology》1987,53(12):2808-2814
Fifteen Bacillus thuringiensis strains representing 13 serotypes were screened with five oligodeoxyribonucleotide probes specific for certain regions of two published sequences and one unpublished sequence of B. thuringiensis delta-endotoxin genes. Of the 15 cultures, 14 hybridized with at least one probe; the B. thuringiensis subsp. thompsoni strain alone did not hybridize. Two B. thuringiensis subsp. kurstaki strains of commercial interest, HD-1 and NRD-12, were found to be so closely related as to be indistinguishable with this technique; the same situation was found with strains from B. thuringiensis subspp. dendrolimus and sotto. Five strains were identified as probably containing only one endotoxin gene. A probe specific for the gene from the B. thuringiensis subsp. kurstaki HD-73 strain hybridized to only 3 of the 15 cultures tested. The hybridization data suggest that the DNA sequences coding for the C-terminal region of the endotoxin protein are as well conserved as those coding for the N-terminal toxic portion. 相似文献
6.
Induction of monocytic differentiation of HL-60 cells by 1,25-dihydroxyvitamin D analogs 总被引:3,自引:0,他引:3
V K Ostrem W F Lau S H Lee K Perlman J Prahl H K Schnoes H F DeLuca 《The Journal of biological chemistry》1987,262(29):14164-14171
1,25-Dihydroxyvitamin D3, the hormonal form of vitamin D, induces differentiation of HL-60 human promyelocytes into monocyte-like cells in vitro. We assessed the relative activity of 30 analogs of 1,25-dihydroxyvitamin D3 in inducing development of monocytic markers in HL-60 cells. The three differentiation markers assayed were nonspecific acid esterase activity, nitro blue tetrazolium reducing activity, and phagocytic capacity. Of the known metabolites of vitamin D, 1,25-dihydroxyvitamin D3 is the most active; 50% of the cells exhibit the mature phenotype following a 4-day treatment with 10(-8) M 1,25-dihydroxyvitamin D3. Removal of either the C-1 or C-25-hydroxyl group reduces activity by 2 orders of magnitude, while epimerization of the 1 alpha- to 1 beta-hydroxyl group virtually abolishes activity. Elongation of the steroidal side chain of 1,25-dihydroxyvitamin D3 by addition of one carbon at C-24 or C-26 improves the potency by an order of magnitude. Truncation of the steroidal side chain leads to a 10-fold reduction in activity for each carbon removed. Elimination of the C-26 and C-27 methyl groups reduces activity 100-fold. Analogs with short aliphatic side chains as 1 alpha-hydroxyhomo- and bishomopregnacholecalciferol have surprisingly high activity, being only 20-fold less potent than the natural hormone. The activity of most analogs in the HL-60 system parallels their known relative affinities for the well characterized 1,25-dihydroxyvitamin D3 receptor in chick intestine, providing further evidence that this function of 1,25-dihydroxyvitamin D3 is receptor mediated. 相似文献
7.
Structural relatedness of lysis proteins from colicinogenic plasmids and icosahedral coliphages 总被引:4,自引:0,他引:4
The host-lysis-inducing functions of phi X174 protein E and MS2 protein L
were recently shown to reside on the N-terminal and C-terminal halves of
the two respective lysis proteins. In the present study it is shown that
the small lysis proteins encoded in various colicinogenic plasmids share
local sequence similarities and certain structural characteristics with the
essential peptides of their coliphage-coded counterparts. Despite their
dissimilar sizes and origins, it is suggested that the colicinogenic lysis
proteins are functionally analogous and evolutionarily related to those of
icosahedral single- stranded DNA and RNA phages.
相似文献
8.
C J Mirell M Yanagisawa R Lau A E Pekary W W Chin J M Hershman 《Molecular endocrinology (Baltimore, Md.)》1987,1(6):408-412
Thyroidectomized rats were used to study the effects of a single injection of T3 on pituitary mRNA synthesis and hormone secretion. T3 was injected ip at doses of 0, 0.2, 1, or 5 micrograms/100 g body weight, and and animals were killed 24 h later. T3 caused a significant decrease in serum TSH, but caused no significant change in either serum GH or PRL. Pituitary mRNA was quantified by slot blot hybridization with cDNA probes specific for alpha-TSH, beta-TSH, PRL, and GH. We found that both the alpha and beta mRNA subunits decreased, that PRL mRNA remained relatively unchanged, and that GH mRNA increased with increasing T3 dose. The data show that a single dose of T3 can profoundly influence mRNA levels in the anterior pituitary; the lowest dose of T3 caused maximum inhibition of alpha-TSH mRNA while beta-TSH mRNA declined further in a dose-dependent manner. 相似文献
9.
Interaction of acyl coenzyme A substrates and analogues with pig kidney medium-chain acyl-coA dehydrogenase 总被引:2,自引:0,他引:2
Several alkylthio coenzyme A (CoA) derivatives (from ethyl- to hexadecyl-SCoA) have been synthesized to probe the substrate binding site in the flavoprotein medium-chain acyl-CoA dehydrogenase from pig kidney. All bind to apparently equivalent sites with a stoichiometry of four per tetramer. A plot of log Kd vs: hydrocarbon chain length is linear from 2 to 16 carbons with a free energy of binding of 390 cal/methylene group. These data suggest an acyl-binding site of moderate hydrophobicity and imply that the observed substrate specificity of the medium-chain dehydrogenase is not achieved simply by the length of the hydrocarbon binding pocket. Extrapolation of the graph to zero chain length predicts a Kd of 1 mM for the CoA moiety. The difference between this value and the experimentally determined value of 206 microM may be attributed to a contribution from the ionization of the sulfhydryl group in CoASH. The interaction of several eight-carbon intermediates of beta-oxidation (trans-2- and trans-3-octenoyl-CoA and L-3-hydroxy- and 3-ketooctanoyl-CoA) with the dehydrogenase has also been studied. All but the L-3-OH derivative bind tightly to the enzyme (with Kd values in the 50-90 nM range) and are very effective inhibitors of the dehydrogenation of octanoyl-CoA. The trans-3-enoyl analogue produces an immediate, intense, long-wavelength band (lambda max = 820 nm), which probably represents a charge-transfer interaction between the delocalized alpha-carbanion donor and oxidized flavin as the acceptor. The L-3-OH analogue is a reductant of the flavin, yielding 3-ketooctanoyl-CoA.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
10.
The testis-specific phosphoglycerate kinase gene pgk-2 is a recruited retroposon. 总被引:15,自引:4,他引:11
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In both humans and mice, two genes encode phosphoglycerate kinase, a key enzyme in the glycolytic pathway. The pgk-1 gene is expressed in all somatic cells, is located on the X chromosome, and contains 10 introns. The pgk-2 gene is expressed only in sperm cells, is located on an autosome, and has no introns. The nucleotide sequence of the pgk-2 gene suggests that it arose from pgk-1 more than 100 million years ago by RNA-mediated gene duplication. The pgk-2 gene may, then, be a transcribed retroposon. Thus, gene duplication by retroposition may have been used as a mechanism for evolutionary diversification. 相似文献