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1.
A. O. Shpakov 《Journal of Evolutionary Biochemistry and Physiology》2002,38(6):650-672
This review summarizes and analyzes data on structural and functional peculiarities of - and -subunits of heterotrimeric G proteins and their participation in -dimer in processes of hormonal signal transduction to the cell. The molecular mechanisms are discussed, which are responsible for formation of the -dimer complex and its interaction with the wide spectrum of signal and structural proteins, such as G protein -subunit, serpentine type receptors, kinases of G protein-coupled receptors, adenylyl cyclase, phospholipase C2, phosphatidyl-inositol-3-kinase, Raf-kinase, potassium and calcium channels, microtubular and RGS-proteins. The characteristics of - and -subunits are given for living organisms of different phylogenetic levels (lower eukaryotes, fungi, plants, vertebrates, and invertebrates). It is concluded that the -dimer is the most important regulatory link in various signal systems to carry out switch from one signal cascade to another and thereby to determine the final cellular response to the signal impulse. 相似文献
2.
Summary An investigation of the stereospecificity of -adrenergic insulin release, its relation to -adrenergic blockade and the adrenergic innervation of the pancreatic islets was performed in the mouse. It was observed that in vivo -adrenergic stimulation of insulin release by isopropylnoradrenaline was stereospecific for the L-stereoisomer and selectively blocked by the L-isomer of the -adrenergic antagonist L-propranolol. D-propranolol had no effect. Pretreatment of mice with a dose of D-isopropylnoradrenaline devoid of insulin releasing activity, slightly increased the subsequent insulin response to a halfmaximal dose of L-isopropylnoradrenaline. Basal insulin secretion was blocked by L-propranolol (-adrenergic blockade) and increased by phentolamine (-adrenergic blockade). A -blocked insulin response to L-isopropyl-noradrenaline could be overcome by -adrenergic blockade depending on the dose of the -agonist, suggesting a close association between the adrenergic receptors.The adrenergic innervation of the islet cells was studied by electron microscopic autoradiography after injection of 3H-L-noradrenaline. It was observed that labelled adrenergic nerve terminals were associated with both A1(D-), A2 and B-cells. The nerves were mainly distributed in the periphery of the islets either as single axons or as bundles. The majority of the terminals were associated with A2-cells, the most frequent cell type in the islet periphery. However, in all islets examined terminals were found close to B-cells. Adrenergic terminals often caused indentations in the contour of an islet cell and were separated from the islet cell membrane only by a narrow intercellular space, about 20 nm in width.It is concluded that the islet cells of the mouse are equipped with the morphological substrate for direct adrenergic regulation. Further it is suggested that the B-cell is supplied with L-stereospecific -adrenergic receptors and that the - and -adrenergic receptors are at least partially interrelated. 相似文献
3.
Tassos P. Anastassiades Ravi K. Chopra Anne Wood 《Molecular and cellular biochemistry》1979,158(1):25-32
In anchorage-dependent (AD) cultures of the outer cell population (OCP) from neonatal rat calvaria, transforming growth factor-1 (TGF-) specifically upregulated the synthesis of chondroitin sulfate (CS) proteoglycan (PG) and uncoupled the inhibitory effect of increasing cell density on CS PG synthesis (reference #30). Utilizing the same cell population, we have further examined the possibility that glycosaminoglycans (GAG) known to be synthesized and secreted by bone cells might exert feedback effects on GAG synthesis and/or its stimulation by TGF-. Although addition of TGF- alone stimulated net synthesis of HA and CS in both AD and anchorage-independent (AI) cultures, significant alterations of basal and TGF--stimulated GAG synthesis by exogenous GAGs were observed only in AI cultures. In AI cultures exogenously added hyaluronic acid (HA) markedly enhanced the basal synthesis of HA and CS while heparin (H) suppressed the basal synthesis of HA, CS as well as dermatan sulfate (DS). Also, the addition of HA markedly potentiated the stimulation by TGF- of HA and CS synthesis as did heparan sulfate (HS) for CS and DS synthesis. H suppressed the stimulation of the synthesis of HA, CS and DS by TGF-. Overall, our results indicate specific effects of individual GAGs on basal and TGF--stimulated GAG synthesis in OCP cultures. We suggest that some of the GAGs in the OCP microenvironment (which with the exception of HA are covalently linked to protein cores of secreted PGs), acting in concert with TGF-, may serve as an amplification system for upregulating GAG synthesis in the rapidly growing neonatal calvarium. 相似文献
4.
Sarah Ehrlich-Rogozinski Antonio De Maio Halina Lis Nathan Sharon 《Glycoconjugate journal》1987,4(4):379-390
The interaction of125I-labeledErythrina cristagalli agglutinin (ECA) with neutral glycosphingolipids on thin layer chromatograms was examined by the overlay technique followed by radioautography. The lectin bound topara-globoside with a sensitivity about 10 times higher than to lactosylceramide or globoside, in agreement with the specificity of the lectin forN-acetyllactosamine. The lower limit of detection ofpara-globoside was about 0.66 nmol. The specific binding of ECA to this glycolipid was confirmed by a highly sensitive enzyme-linked lectin assay (ELLA), utilizing the horseradish peroxidase-avidin-biotin system for detection of bound lectin. Overlays of neutral glycosphingolipid extracts from human erythrocyte membranes and from human granulocytes with ECA demonstrated that the lectin can be employed for the detection of small amounts ofpara-globoside in biological materials also in the presence of excess globoside. No staining was obtained when thin layer chromatograms of neutral glycosphingolipid extracts from rabbit erythrocyte membranes were overlayed with125I-ECA. Afterin situ treatment of the chromatograms with -galactosidase, the lectin bound to several components, one of which had a mobility corresponding to that of the pentahexosylceramide Gal3Gal4GlcNAc3Gal4Glc1Cer, the major neutral glycosphingolipid of rabbit erythrocytes, thus providing further evidence for the specificity of ECA forpara-globoside.Abbreviations GSL
glycosphingolipid(s)
- CDH
lactosylceramide, Gal4Glc1Cer
- CTH
trihexosylceramide, Gal4Gal4Glc1Cer
- GLOB
globoside, GalNac3Gal4Gal4Glc1Cer
- PG
para-globoside, Gal4GlcNAc3Gal4Glc1Cer
- AsGM1
asialo-GM1, Gal3GalNAc4Gal4Glc1Cer
- FORS
Forsmann antigen, GalNAc3GalNAc3Gal4Gal4Glc1Cer
- CPH
pentahexosylceramide, Gal3Gal4GlcNAc3Gal4Glc1Cer
- ECA
Erythrina cristagalli agglutinin
- SBA
soybean agglutinin
- PBS
phosphate-buffered saline
- PVP-40
polyvinylpyrrolidone M.W. 40000
- BSA
bovine serum albumin
- HRP-avidin
horseradish peroxidase conjugated to avidin
- ELLA
enzyme-linked lectin assay
- ELISA
enzyme-linked immunosorbent assay
- PMNL
polymorphonuclear leukocytes
- HPTLC
high performance thin layer chromatography 相似文献
5.
D. McKay Hart 《Histochemistry and cell biology》1966,6(1):17-23
Summary The histochemical distribution of various hydroxysteroid dehydrogenases in human, term, foetal membranes has been investigated using the tetrazolium dye, Nitro-B.T.The trophoblastic layer was the most active, showing 3-, 3-, 11-, 16- and 17-hydroxysteroid dehydrogenase activities, a pattern of activity similar to that of the placental villous trophoblast.The amniotic epithelium showed weak 3-, 3-, 16- and 17-hydroxysteroid dehydrogenase activity; weak 3- and 3-hydroxysteroid dehydrogenase activity was noted in the connective tissue layers.All activity demonstrated was N.A.D.-linked. 相似文献
6.
Ralph Kirby 《Journal of molecular evolution》1992,34(4):345-350
Summary The protein sequences of 18 class A -lactamases and 2 class C -lactamases were analyzed to produce a rooted phylogenetic tree using the DD peptidase of Streptomyces R61 as an outgroup. This tree supports the penicillin-binding proteins as the most likely candidate for the ancestoral origin of the class A and class C -lactamases, these proteins diverging from a common evolutionary origin close to the DD peptidase. The actinomycetes are clearly shown as the origin of the class A -lactamases found in other non-actinomycete species. The tree also divides the -lactamases from the Streptomyces into two subgroups. One subgroup is closer to the DD peptidase root. The other Streptomyces subgroup shares a common branch point with the rest of the class A -lactamases, showing this subgroup as the origin of the non-actinomycete class A -lactamases. The non-actinomycete class A -lactamase phylogenetic tree suggests a spread of these -lactamases by horizontal transfer from the Streptomyces into the non-actinomycete gram-positive bacteria and thence into the gram-negative bacteria. The phylogenetic tree of the Streptomyces class A -lactamases supports the possibility that horizontal transfer of class A -lactamases occurred within the Streptomyces. 相似文献
7.
Sachio Hayashi Takenobu Yoshiyama Norito Fujii Satoru Shinohara 《Biotechnology letters》2000,22(18):1465-1469
A novel syrup containing neofructo-oligosaccharides was produced from sucrose (Brix 70) by whole cells of Penicillium citrinum. The efficiency of fructo-oligosaccharides production was more than 55% and those of the main carbohydrate components, 1-kestose (Fruf 21Fruf 21 Glc), nystose (Fruf 21Fruf 21 Fruf 21 Glc) and neokestose (Fruf 26 Glc12 Fruf), were 22, 14 and 11%, respectively. 相似文献
8.
A. D. Baxter A. H. Baillie M. M. Ferguson G. P. Lewis 《Histochemistry and cell biology》1966,7(3):218-223
Summary In these experiments, a considerable range of hydroxysteroid dehydrogenases were demonstrated in vertebrate hepatic tissue; 3, 3, 6, 11, 16, 16, 17 and 20 were consistently present.3 hydroxysteroid dehydrogenase was fairly active in mammalian liver, but consistently greater activity was seen with the 3 dehydrogenases which are probably concerned with steroid detoxication and excretion. 6 and 11 hydroxysteroids were only moderately well used, and both these were noticeably better used in male tissue, as were also 3, 3, 16 and 16 hydroxysteroids. All mammalian liver utilised 16, 16 and 17 compounds fairly well, and 20 was consistently but poorly used.This histochemical evidence agrees with biochemical and clinical evidence for the significance and nature of steroid metabolism in the liver. Many of the enzymes showing activity in the liver have known function in the detoxication and elimination of steroids; and 3-hydroxysteroid dehydrogenase is concerned in cholesterol biosynthesis as well as the biosynthesis of progesterane. To have shown contrasting patterns of activity between liver and steroid producing endocrine tissues is further evidence for the specificity of these techniques in the study of dehydrogenase distribution. 相似文献
9.
H. S. Kwan K. H. So K. Y. Chan S. C. Cheng 《World journal of microbiology & biotechnology》1993,9(1):50-52
An isolate from a Hong Kong soil sample which produced -amylase was identified as a thermotolerant strain ofBacillus circulans with a growth range of 35 to 55C. The -amylase was stable at 45°C for 30 min but lost half of its activity after 30 min at 50°C. Maximum specific activity of -amylase (36.2 units/mg protein) in the culture broth was detected after 36 h of cultivation at 45°C in a medium containing soluble starch, beef extract, coconut water and inorganic salts. 相似文献
10.
Summary The in vitro transformation of pregnenolone into progesterone in Digitalis lanata tissues was shown to be catalyzed by a 3-hydroxysteroid dehydrogenase/ketosteroid isomerase (3-HSD). Product formation was monitored by HPLC. The enzyme could be partially characterized and 3-HSD activities were measured in various Digitalis lanata tissues and in cell cultures of other plant species. Since no correlation was observed between biosynthetic competence of the tissue and 3-HSD activity, it was concluded that this enzyme does not play a major role in regulating cardenolide biosynthesis.Abbreviations BA
benzyladenine
- 2,4-D
2,4-dichlorophenoxyacetic acid
- DMSO
dimethyl sulfoxide
- DMF
N,N-dimethylformamide
- IAA
indole-3-acetic acid 相似文献
11.
I. S. Sever E. S. Kalyaeva O. N. Danilevskaya Zh. M. Gorlenko 《Molecular & general genetics : MGG》1982,188(3):494-498
Summary An opr24 mutation decreasing the degradation of RNA polymerase subunits was found among the Ts+ revertants of Ts strain carring an rpoC1 mutation which stimulates overproduction of these polypeptides. The opr24 mutation is allele-non-specific, for it decreases the degradation of the mutant and subunits, the amberfragment of the subunit and the non-mutant subunit. Moreover, opr24 reduces the proteolysis of abnormal proteins containing canavanine.The opr24 mutation maps between 17 and 21 min on the E. coli genetic map.The results demonstrate that a slow proteolysis rate in the bacterial cell can supress conditional lethal mutations.In addition, the slower degradation and the ensuing accumulation of subunits does not effect the rate of the subunit synthesis. 相似文献
12.
Endo--galactosidase (EC 3.2.1.103) ofBacteroides fragilis, at 250 mU ml–1, did not cleave the internal galactosidic linkage of the linear radiolabelled trisaccharide GlcNAc1-6Gal1-4GlcNAc, or those of the tetrasaccharides Gal1-4GlcNAc1-6Gal1-4GlcNAc and Gal1-4GlcNAc1-6Gal1-4Glc. The isomeric glycans which contained the GlcNAc1-3Gal1-4GlcNAc/Glc sequence were readily cleaved.Abbreviations GlcNAc
2-acetamido-2-deoxy-d-glucose
- Lact
lactose
- MT
maltotriose
- MTet
maltotetraose
-
R
MTet
chromatographic migration rate in relation to that of maltotetraose 相似文献
13.
A new -glucosidase was partially purified from Trichoderma viride cellulase. This -glucosidase catalyzed a transglycosylation reaction of cellobiose to give -D-Glc-(16)--D-Glc-(14)-D-Glc (1, yield: 18.8%) and -D-Glc-(16)--D-Glc-(16)--D-Glc-(14)-D-Glc (2, 3.7%), regioselectively. Furthermore, the enzyme regioselectively converted laminaribiose and gentiobiose into -D-Glc-(16)--D-Glc-(13)-D-Glc (3, 15.3%) and -D-Glc-(16)--D-Glc-(16)-D-Glc (4, 20.2%), respectively. The structures (1–4) of the products were determined by 1H and 13C NMR spectroscopies. This high regio- and stereoselectively of the -glucosidase could be applied for oligosaccharide synthesis. 相似文献
14.
Summary Two double heterozygous 0/0 thalassemic sibs of Mexican descent were studied. The father had a 0/0 genotype, while the mother, one sib and several maternal relatives were 0/0 heterozygotes. Parental consanguinity and an apparently low frequency of thalassemia among Mexicans suggested a possible common origin of both 0 and 0 genes. A hypothesis to explain such a possibility is proposed on the basis of a partial mispairing between 0 and genes followed by a crossing-over which would results in a 0 recombinant gene. This hypothesis could also be extended to explain the 22 gluala, 22 alaglu and 116 arghis Hb variants as recombinants from double crossing-over between and mispaired genes for which the name interstitial-Lepore is proposed. 相似文献
15.
Oxysterols have been shown to induce apoptosis in a variety of cell lines. The mechanism of oxysterol-induced apoptosis is mainly known at the post-mitochondrial level. The aim of the present study was to compare the pathway of apoptosis induced by the oxysterols 7-hydroxycholesterol (7-OH) and cholesterol-5,6-epoxide (-epoxide) in U937 cells. To this end, we employed a range of inhibitors of apoptosis; a broad-spectrum caspase inhibitor, a specific caspase-3 inhibitor and an inhibitor of cytochromec release and the antioxidants; trolox, ebselen and resveratrol. The three inhibitors of apoptosis prevented cell death induced by 7-OH; however, in -epoxide-treated cells, the inhibitor of cytochromec release did not protect against apoptosis. The cellular antioxidant glutathione was depleted in 7-OH-treated cells but not in cells incubated with -epoxide. Trolox, a water-soluble synthetic analogue of -tocopherol, prevented 7-OH-induced apoptosis but did not protect against cell death induced by -epoxide. Ebselen and resveratrol did not protect U937 cells against apoptosis induced by either 7-OH or -epoxide. Our results suggest that differences occur in the pathways of apoptosis induced by 7-OH and -epoxide in U937 cells. 相似文献
16.
Summary The and subunit of RNA polymerase are thought to be controlled by a translational feedback mechanism regulated by the concentration of RNA polymerase holoenzyme. To study this regulation in vivo, an inducible RNA polymerase overproduction system was developed. This system utilizes plasmids from two incompatibility groups that carry RNA polymerase subunit genes under lac promoter/operator control. When the structural genes encoding the components of core RNA polymerase (, and ) or holoenzyme (, , and 70) are present on the plasmids, induction of the lac promoter results in a two fold increase in the concentration of functional RNA polymerase. The induction of RNA polymerase overproduction is characterized by an initial large burst of synthesis followed by a gradual decrease as the concentration of RNA polymerase increases. Overproduction of RNA polymerase in a strain carrying an electrophoretic mobility mutation in the rpoB gene results in the specific repression of synthesis off the chromosome. These results indicate that RNA polymerase feedback regulation controls synthesis in vivo. 相似文献
17.
Kusaykin MI Burtseva YV Svetasheva TG Sova VV Zvyagintseva TN 《Biochemistry. Biokhimii?a》2003,68(3):317-324
The distribution of O-glycosylhydrolases (fucoidan hydrolases, -D-mannosidases, -D-glucosidases, and -D-galactosidases) in 30 species of marine invertebrates occurring in the Sea of Japan was studied. It is shown that fucoidanases and glycosidases are widespread in the animals analyzed. Some molluscan, annelid, and echinoderm species can probably serve as objects for isolation and detailed study of the fucoidan-hydrolyzing enzymes. Fucoidan hydrolase, -L-fucosidase, and arylsulfatase from the marine mollusk Littorina kurila were isolated and described. It was found that -L-fucosidase and arylsulfatase hydrolyze synthetic substrates and cannot hydrolyze natural fucoidan, whereas fucoidan hydrolase cleaves fucoidan to produce sulfated oligosaccharides and fucose. 相似文献
18.
S. -J. Yin W. F. Bosron T. -K. Li K. Ohnishi K. Okuda H. Ishii M. Tsuchiya 《Biochemical genetics》1984,22(1-2):169-180
Liver homogenate-supernatants from most Japanese exhibit an atypical pH optimum for ethanol oxidation at pH 8.8 instead of 10.5, the typical pH-activity optimum. It has been proposed that atypical livers contain alcohol dehydrogenase isozymes with 2 subunits while typical livers contain isozymes with 1 subunits, both produced by the ADH
2 gene. Because it is difficult to differentiate the atypical ADH2 2-2 phenotype from the ADH2 2-1 phenotype by starch gel electrophoresis, an agarose isoelectric focusing procedure was developed that clearly separated the atypical Japanese livers into two groups, A1 and A2. The isozymes in A1 and A2 livers were purified. Type A1 livers contained a single isozyme with an atypical pH-rate profile; it was designated 22. Three isozymes were isolated from A2 livers, two of which corresponded to 11 and 22. A third, absent from the typical and the atypical A1 livers, had an intermediate mobility; it was designated 21. Type A1 livers are, therefore, the homozygous ADH2 2-2 phenotype, and type A2 livers, the heterozygous ADH2 2-1 phenotype. The ADH2 2-2 phenotype was found in 53% of 194 Japanese livers, and the ADH2 2-1 phenotype, in 31%. Accordingly, the frequency of ADH
2
2
was 0.68.This study was supported by U.S. Public Health Service Grant AA 02342. 相似文献
19.
Geert L. M. van Rens Frans A. Hol Wilfried W. de Jong Hans Bloemendal 《Journal of molecular evolution》1991,33(5):457-463
Summary The eye lens-crystallins in cow and chicken are encoded by a family of at least six genes. In order to assess the distribution of the corresponding genes among other vertebrates we hybridized -crystallin sequences (A2, A3/A1, A4, B1, B2, B3), isolated from a bovine lens cDNA library, to Southern blots on whichEcoR1-digested chromosomal DNA was blotted from different vertebrate species. These included human, chimpanzee, calf, rat, pigeon, duck, monitor lizard, toad, trout, and lamprey. Positive hybridization signals were found in the representatives of virtually all classes of vertebrates. The basic B-crystallins gave hybridization signals in more species than the acidic A ones. In monitor lizard and toad the weakest hybridization signals for basic crystallin probes were found. For acidic crystallin probes the distribution pattern was more simple; among cold-blooded vertebrates a signal for A2 was found in trout and lamprey, for A4 in trout, and for A3/A1 only in toad. The results demonstrate that the duplications leading to the -crystallin gene family occurred before or during the earliest stages of vertebrate evolution. 相似文献
20.
-N-Acetyl-d-hexosaminidase from Aspergillus oryzae catalysed the stereo- and regiospecific formation of the 6-O-benzylated disaccharide derivatives GalNAc1-3(6- OBn)Gal-SEt and GlcNAc1-3(6-OBn)Gal-SEt, which were obtained in transglycosylation reactions employing ethyl 6- O-benzyl-1-thio--d-galactopyranoside as acceptor. Preparative amounts of the chitobiose derivative GlcNAc1- 3GlcNAc-OPhNO2-p was prepared as well. - N-Acetyl-d-hexosaminidase from bovine testes catalysed the specific synthesis of GlcNAc1-3(6-OBn)GlcNH2-SEt and GalNAc1-3(6-OBn)GlcNH2-SEt, employing ethyl 2-amino-6-O-benzyl-2-deoxy-1-thio--d-glucopyranoside as acceptor. -d-Glucuronidase from E. coli was found to catalyse the formation of GlcA1-3(6-OBn)GlcNH2- SEt employing the same acceptor. 相似文献