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1.
Jun Li Chang-Lei Deng Fang Gao Jiu-Hua Cheng Zhi-Bin Yu Li Liu Man-Jiang Xie 《Molecular and cellular biochemistry》2009,331(1-2):117-126
Large-conductance Ca2+-activated K+ channel is formed by a tetramer of the pore-forming α-subunit and distinct accessory β-subunits (β1–β4) which contribute to BKCa channel molecular diversity. Accumulative evidences indicate that not only α-subunit alone but also the α + β subunit complex and/or β-subunit might play an important role in modulating various physiological functions in most mammalian cells. To evaluate the detailed pharmacological and biophysical properties of α + β1 subunit complex or β1-subunit in BKCa channel, we established an expression system that reliably coexpress hSloα + β1 subunit complex in HEK293 cells. The coexpression of hSloα + β1 subunit complex was evaluated by western blotting and immunolocalization, and then the single-channel kinetics and pharmacological properties of expressed hSloα + β1 subunit complex were investigated by cell-attached and outside-out patches, respectively. The results in this study showed that the expressed hSloα + β1 subunit complex demonstrated to be fully functional for its typical single-channel traces, Ca2+-sensitivity, voltage-dependency, high conductance (151 ± 7 pS), and its pharmacological activation and inhibition. 相似文献
2.
Nasiara Karim Petrine Wellendorph Nathan Absalom Graham A. R. Johnston Jane R. Hanrahan Mary Chebib 《Amino acids》2013,44(4):1139-1149
GABAA receptors are members of the ligand-gated ion channel superfamily that mediate inhibitory neurotransmission in the central nervous system. They are thought to be composed of 2 alpha (α), 2 beta (β) subunits and one other such as a gamma (γ) or delta (δ) subunit. The potency of GABA is influenced by the subunit composition. However, there are no reported systematic studies that evaluate GABA potency on a comprehensive number of subunit combinations expressed in Xenopus oocytes, despite the wide use of this heterologous expression system in structure–function studies and drug discovery. Thus, the aim of this study was to conduct a systematic characterization of the potency of GABA at 43 human recombinant GABAA receptor combinations expressed in Xenopus oocytes using the two-electrode voltage clamp technique. The results show that the α-subunits and to a lesser extent, the β-subunits influence GABA potency. Of the binary and ternary combinations with and without the γ2L subunit, the α6/γ2L-containing receptors were the most sensitive to GABA, while the β2- or β3-subunit conferred higher sensitivity to GABA than receptors containing the β1-subunit with the exception of the α2β1γ2L and α6β1γ2L subtypes. Of the δ-subunit containing GABAA receptors, α4/δ-containing GABAA receptors displayed highest GABA sensitivity, with mid-nanomolar concentrations activating α4β1δ and α4β3δ receptors. At α4β2δ, GABA had low micromolar activity. 相似文献
3.
Oversaturated deoxy-α2β2T4V aggregated instantly without a delay time, which is in contrast to the delay time before the generation of fibers of deoxy-HbS and deoxy-α2β2E6V,D73H. Solubility of deoxy-α2β2T4V was ∼10-fold lower than that of deoxy-HbS and was similar to oxy- and deoxy-α2β2E6V,T4V. These results indicate that β4Val in HbA in the oxy and deoxy forms with or without β6Val facilitates hydrophobic interaction of the A-helix with the EF helix of adjacent molecules without forming a β4/β73 hydrogen bond. Deoxy-HbA generated crystals following aggregation as does HbC-Harlem(α2β2E6V,D73N), while α2β2T4V and α2β2D73H as well as HbS, α2β2E6V,D73H and α2β2E6V,T4V in the oxy and deoxy forms did not form crystals, indicating in addition to the strength of β6 amino acid hydrophobicity that the synergism between the β4Thr hydrogen bond and β6 hydrophobic interaction free energies on the A-helix play a critical role in formation of fibers versus crystalline nuclei during phase transition. 相似文献
4.
F.J. Lopez Aparicio F. Zorrilla Benitez F. Santoyo Gonzalez 《Carbohydrate research》1983,114(2):297-302
β-d-Mannosidase (β-d-mannoside mannohydrolase EC 3.2.1.25) was purified 160-fold from crude gut-solution of Helix pomatia by three chromatographic steps and then gave a single protein band (mol. wt. 94,000) on SDS-gel electrophoresis, and three protein bands (of almost identical isoelectric points) on thin-layer iso-electric focusing. Each of these protein bands had enzyme activity. The specific activity of the purified enzyme on p-nitrophenyl β-d-mannopyranoside was 1694 nkat/mg at 40° and it was devoid of α-d-mannosidase, β-d-galactosidase, 2-acet-amido-2-deoxy-d-glucosidase, (1→4)-β-d-mannanase, and (1→4)-β-d-glucanase activities, almost devoid of α-d-galactosidase activity, and contaminated with <0.02% of β-d-glucosidase activity. The purified enzyme had the same Km for borohydride-reduced β-d-manno-oligosaccharides of d.p. 3–5 (12.5mm). The initial rate of hydrolysis of (1→4)-linked β-d-manno-oligosaccharides of d.p. 2–5 and of reduced β-d-manno-oligosaccharides of d.p. 3–5 was the same, and o-nitrophenyl, methylumbelliferyl, and naphthyl β-d-mannopyranosides were readily hydrolysed. β-d-Mannobiose was hydrolysed at a rate ~25 times that of 61-α-d-galactosyl-β-d-mannobiose and 63-α-d-galactosyl-β-d-mannotetraose, and at ~90 times the rate for β-d-mannobi-itol. 相似文献
5.
Macarena Rojas Pablo Díaz Pablo León Alexis A. Gonzalez Magdalena González Víctor Barrientos 《Channels (Austin, Tex.)》2017,11(5):388-398
Renal sodium reabsorption depends on the activity of the Na+,K+-ATPase α/β heterodimer. Four α (α1–4) and 3 β (β1–3) subunit isoforms have been described. It is accepted that renal tubule cells express α1/β1 dimers. Aldosterone stimulates Na+,K+-ATPase activity and may modulate α1/β1 expression. However, some studies suggest the presence of β3 in the kidney. We hypothesized that the β3 isoform of the Na+,K+-ATPase is expressed in tubular cells of the distal nephron, and modulated by mineralocorticoids. We found that β3 is highly expressed in collecting duct of rodents, and that mineralocorticoids decreased the expression of β3. Thus, we describe a novel molecular mechanism of sodium pump modulation that may contribute to the effects of mineralocorticoids on sodium reabsorption. 相似文献
6.
James R Trudell 《生物化学与生物物理学报:生物膜》2002,1565(1):91-96
Recent publications defined requirements for inter-subunit contacts in a benzodiazepine-sensitive GABAA receptor (GABAARα1β3γ2). There is strong evidence that the heteropentameric receptor contains two α1, two β3, and one γ2 subunit. However, the available data do not distinguish two possibilities: When viewed clockwise from an extracellular viewpoint the subunits could be arranged in either γ2β3α1β3α1 or γ2α1β3α1β3 configurations. Here we use molecular modeling to thread the relevant GABAAR subunit sequences onto a template of homopentameric subunits in the crystal structure of the acetylcholine binding protein (AChBP). The GABAA sequences are known to have 15-18% identity with the acetylcholine binding protein and nearly all residues that are conserved within the nAChR family are present in AChBP. The correctly aligned GABAA sequences were threaded onto the AChBP template in the γ2β3α1β3α1 or γ2α1β3α1β3 arrangements. Only the γ2α1β3α1β3 arrangement satisfied three known criteria: (1) α1 His102 binds at the γ2 subunit interface in proximity to γ2 residues Thr142, Phe77, and Met130; (2) α1 residues 80-100 bind near γ2 residues 91-104; and (3) α1 residues 58-67 bind near the β3 subunit interface. In addition to predicting the most likely inter-subunit arrangement, the model predicts which residues form the GABA and benzodiazepine binding sites. 相似文献
7.
Tadasu Urashima Emi Yamaguchi Takeharu Ohshima Kenji Fukuda Tadao Saito 《Glycoconjugate journal》2018,35(3):275-286
In this study on milk saccharides of the raccoon (Procyonidae: Carnivora), free lactose was found to be a minor constituent among a variety of neutral and acidic oligosaccharides, which predominated over lactose. The milk oligosaccharides were isolated from the carbohydrate fractions of each of four samples of raccoon milk and their chemical structures determined by 1H-NMR and MALDI-TOF mass spectroscopies. The structures of the four neutral milk oligosaccharides were Fuc(α1–2)Gal(β1–4)Glc (2′-fucosyllactose), Fuc(α1–2)Gal(β1–4)GlcNAc(β1–3)Gal(β1–4)Glc (lacto-N-fucopentaose IV), Fuc(α1–2)Gal(β1–4)GlcNAc(β1–3)Gal(β1–4)GlcNAc(β1–3)Gal(β1–4)Glc (fucosyl para lacto-N-neohexaose) and Fuc(α1–2)Gal(β1–4)GlcNAc(β1–3)[Fuc(α1–2)Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (difucosyl lacto-N-neohexaose). No type I oligosaccharides, which contain Gal(β1–3)GlcNAc units, were detected, but type 2 saccharides, which contain Gal(β1–4)GlcNAc units were present. The monosaccharide compositions of two of the acidic oligosaccharides were [Neu5Ac]1[Hex]6[HexNAc]4[deoxy Hex]2, while those of another two were [Neu5Ac]1[Hex]8[HexNAc]6[deoxy Hex]3. These acidic oligosaccharides contained α(2–3) or α(2–6) linked Neu5Ac, non reducing α(1–2) linked Fuc, poly N-acetyllactosamine (Gal(β1–4)GlcNAc) and reducing lactose. 相似文献
8.
《生物化学与生物物理学报:生物膜》1985,817(1):165-173
The orientation of amino groups in the membrane in the α- and β-subunits of (Na+ + K+)-ATPase was examined by labeling with Boldon-Hunter reagent, N-succinimidyl 3-(4-hydroxy,5-[125I]iodophenyl)propionate), in right-side-out vesicles or in open membrane fragments from the thick ascending limbs of the Henles loop of pig kidney. Sealed right-side-out vesicles of basolateral membranes were separated from open membrane fragments by centrifugation in a linear metrizamide density gradient. After labeling, (Na+ + K+)-ATPase was purified using a micro-scale version of the ATP-SDS procedure. Distribution of label was analyzed after SDS-gel electrophoresis of α-subunit, β-subunit and proteolytic fragments of α-subunit. Both the α- and the β-subunit of (Na+ + K+)-ATPase are uniformly labeled, but the distribution of labeled residues on the two membrane surfaces differs markedly. All the labeled residues in the β-subunit are located on the extracellular surface. In the α-subunit, 65–80% of modified groups are localized to the cytoplasmic surface and 20–35% to the extracellular membrane surface. Proteolytic cleavage provides evidence for the random distribution of 125I-labeling within the α-subunit. The preservation of (Na+ + K+)-ATPase activity and the observation of distinct proteolytic cleavage patterns of the E1- and E2-forms of the α-subunit show that the native enzyme structure is unaffected by labeling with Bolton-Hunter reagent. Bolton-Hunter reagent was shown not to permeate into sheep erythrocytes under the conditions of the labeling experiment. The data therefore allow the conclusion that the mass distribution is asymmetric, with all the labeled amino groups in the β-subunit being on the extracellular surface, while the α-subunit exposes 2.6-fold more amino groups on the cytoplasmic than on the extracellular surface. 相似文献
9.
《Cell communication & adhesion》2013,20(5):403-415
Integrins mediate leukocyte adhesion to vascular endothelium and thereby influence leukocyte recirculation. We have explored expression by peripheral blood T cells of β1 and β7 integrins, particularly α4β1 (VLA-4, CD49d), α4β7 (LPAM-1) and α6β1 (VLA-6, CD49f). Integrin expression differs between CD4+ cells and CD8+ cells in that CD4+ cells: 1) are more heterogeneous, particularly for α4; 2) express on the average less α4 and β7; and 3) express on the average more α6 and β1.2D gel electrophoretic analysis was combined with flow cytometric analysis to determine which integrin chain pairs are expressed by the CD45RO – (naive) and CD45RO+ (memory) subsets of CD4+ cells. CD45RO– (naive) cells express homogeneously at intermediate levels the three integrin pairs α6β1, α4β1 and α4β7. Although 2D gel analysis suggests similar average integrin chain composition for CD45RO+CD4+ (memory) cells, flow cytometric analysis demonstrates multiple subsets of CD45RO+ cells differing markedly from each other and from naive cells in levels of expression of α6 and α4 integrins. There are a minimum of three CD45RO+ subsets: 1) α4β1hiα6β1hiα4β7neg which comprises the majority of memory cells; 2) α4β7hiα6β1low presumptive gut-homing memory cells; and 3) α6β1hiα4β7negα4β1neg, a previously unidentified subset expected to have unique migrational-functional properties. Of particular importance in these results are: the expression by CD4+ naive cells of α6β1, α4β1 and α4β7, the overall prominence and regulation of α6β1 on CD4+ cells, and the selective decreases as well as increases in α4β7 and α4β1 during CD4+ memory specialization. Taken together, these results suggest that differential regulation of expression of α4 and α6 integrin chains that accompany naive-to-memory transition in CD4+ cells are instrumental in generating functional subsets of CD4+ memory cells with specialized recirculation abilities. 相似文献
10.
《Bioscience, biotechnology, and biochemistry》2013,77(11):2406-2411
α-D-Mannosyl-maltotriose (Man-G3) were synthesized from methyl α-mannoside and maltotriose by the transfer action of α-mannosidase. (Man-G3)-βCD and (Man-G3)2-βCD were produced in about 20% and 4% yield, respectively when Aerobacter aerogenes pullulanase (160 units per 1 g of Man-G3) was incubated with the mixture of 1.6 M Man-G3 and 0.16 M βCD at 50°C for 4 days. The reaction products, (Man-G3)-βCD were separated to three peaks by HPLC analysis on a YMC-PACK A-323-3 column and (Man-G3)2-βCD were separated to several peaks by HPLC analysis on a Daisopak ODS column. The major product of (Man-G3)-βCDs was identified as 6-O-α-(63-O-α-D-mannosyl-maltotriosyl)-βCD by FAB-MS and NMR spectroscopies. The structures of (Man-G3)2-βCDs were analyzed by TOF-MS and NMR spectroscopies, and confirmed by comparison of elution profiles of their hydrolyzates by α-mannosidase and glucoamylase on a graphitized carbon column with those of the authentic di-glucosyl-βCDs. The structures of three main components of (Man-G3)2-βCDs were identified as 61,62-, 61,63- and 61,64-di-O-(63-O-α-D-mannosyl-maltotriosyl)-βCD. 相似文献
11.
The (β/α)8‐barrel is one of the most abundant folds found in enzymes. To identify the independent folding units and the segment(s) that correspond to a minimum core structure within a (β/α)8‐barrel protein, fragmentation experiments were performed with Escherichia coli phosphoribosylanthranilate isomerase, which has a single (β/α)8‐barrel domain. Our previous studies indicated that the central four β/α segments comprise an independent folding unit; whereas, the role(s) of the first two β/α segments in folding had not been clarified prior to this report. Herein, we report the design and synthesis of a series of N‐terminally deleted fragments starting with (β/α)1–5β6 as the parent construct. Analytical gel filtration and urea‐induced equilibrium unfolding experiments indicated that deletions within the N‐terminal region, that is, within the first two β/α modules, resulted in reduced stability or aggregation of the remaining segments. The (β/α)3–5β6 segment appeared to fold into a stable structure and deletion of β6 from (β/α)3–5β6 yielded (β/α)3–5, which did not form native‐like secondary structures. However, urea‐induced unfolding of (β/α)3–5, monitored by reduction of tryptophan fluorescence, indicated that the fragment contained a loosely packed hydrophobic core. Taken together, the results of our previous and present fragmentation experiments suggest the importance of the central (β/α)3–4β5 module in folding, which is a finding that is compatible with our simulated unfolding study performed previously. Proteins 2010. © 2010 Wiley‐Liss, Inc. 相似文献
12.
Kang HK Cha H Yang TJ Park JT Lee S Kim YW Auh JH Okada Y Kim JW Cha J Kim CH Park KH 《Biochemical and biophysical research communications》2008,366(1):98-103
Di-O-α-maltosyl-β-cyclodextrin ((G2)2-β-CD) was synthesized from 6-O-α-maltosyl-β-cyclodextrin (G2-β-CD) via a transglycosylation reaction catalyzed by TreX, a debranching enzyme from Sulfolobus solfataricus P2. TreX showed no activity toward glucosyl-β-CD, but a transfer product (1) was detected when the enzyme was incubated with maltosyl-β-CD, indicating specificity for a branched glucosyl chain bigger than DP2. Analysis of the structure of the transfer product (1) using MALDI-TOF/MS and isoamylase or glucoamylase treatment revealed it to be dimaltosyl-β-CD, suggesting that TreX transferred the maltosyl residue of a G2-β-CD to another molecule of G2-β-CD by forming an α-1,6-glucosidic linkage. When [14C]-maltose and maltosyl-β-CD were reacted with the enzyme, the radiogram showed no labeled dimaltosyl-β-CD; no condensation product between the two substrates was detected, indicating that the synthesis of dimaltosyl-β-CD occurred exclusively via transglycosylation of an α-1,6-glucosidic linkage. Based on the HPLC elution profile, the transfer product (1) was identified to be isomers of 61,63- and 61,64-dimaltosyl-β-CD. Inhibition studies with β-CD on the transglycosylation activity revealed that β-CD was a mixed-type inhibitor, with a Ki value of 55.6 μmol/mL. Thus, dimaltosyl-β-CD can be more efficiently synthesized by a transglycosylation reaction with TreX in the absence of β-CD. Our findings suggest that the high yield of (G2)2-β-CD from G2-β-CD was based on both the transglycosylation action mode and elimination of the inhibitory effect of β-CD. 相似文献
13.
R.W. Kirby A. Martelli V. Calderone N.G. McKay K. Lawson 《Bioorganic & medicinal chemistry》2013,21(14):4186-4191
Large conductance calcium activated potassium channels (BKCa) are fundamental in the control of cellular excitability. Thus, compounds that activate BKCa channels could provide potential therapies in the treatment of pathologies of the cardiovascular and central nervous system. A series of novel N-arylbenzamide compounds, and the reference compound NS1619, were evaluated for BKCa channel opener properties in Human Embryonic Kidney (HEK293) cells expressing the human BKCa channel α-subunit alone or α + β1-subunit complex.Channel activity was determined using a non-radioactive Rb+ efflux assay to construct concentration effect curves for each compound. All N-arylbenzamide compounds and NS1619 evoked significant (p <0.05) concentration related increases in Rb+ efflux both in cells expressing α-subunit alone or α + β1-subunits. Co-expression of the β1-subunit modified the Rb+ efflux responses, relative to that obtained in cells expressing the α-subunit alone, for most of the N-arylbenzamide compounds, in contrast to NS1619. The EC40 values of NS1619, BKMe1 and BKOEt1 were not significantly affected by the co-expression of the BKCa channel α + β1-subunits. In contrast, 5 other N-arylbenzamides (BKPr2, BKPr3, BKPr4, BKH1 and BKVV) showed a significant (p <0.05) 2- to 10-fold increase in EC40 values when tested on the BKCa α + β1-subunit expressing cells compared to BKCa α-subunit expressing cells. Further, the Emax values for BKPr4, BKVV and BKH1 were lower in the BKCa channel α + β1-subunit expressing cells.In conclusion, the N-arylbenzamides studied, like NS1619, were able to activate BKCa channels formed of the α-subunit only. The co-expression of the β1-subunit, however, modified the ability of certain compounds to active the channel leading to differentiated pharmacodynamic profiles. 相似文献
14.
《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1999,724(1):65-72
Nicotinic acetylcholine receptor (nAChR) α3-subunits, β4-subunits, α3/β4-subunit combination and α4/β2-subunit combination were immobilized on chromatographic stationary phases and the binding affinities of the different nAChR subtypes were chromatographically evaluated. The observed relative binding affinities of epibatidine were α4/β2>α3/β4 and epibatidine did not bind at α3-subunits and β4-subunits. No significant difference in binding affinities was observed on the α4/β2 nAChRs immobilized in immobilized artificial membrane (IAM) particles and those sterically immobilized on Superdex 200 beads. The effects of mobile phase pH and ionic strength on the binding affinities of the α3/β4 nAChRs support were also investigated. The results are consistent with the proposed ligand–nAChR binding model in which a cationic center exists at the binding site. 相似文献
15.
James A. Ferry Ralph C. Nichols Susan J. Condon John D. Stubbs Sarane T. Bowen 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,739(3):249-257
Previous studies have shown that in the brine shrimp there are three dimeric hemoglobins with polypeptide composition α2, αβ, β2. Concentrations of the α- and β-polypeptides increase in hypoxia. We now report a two-dimensional electrophoretic method for assay of radiolabelled polypeptidesin each hemoglobin. Net synthesis (synthesis minus degradation) of the β-chain, relative to that of the α-chain, increases more than 3-fold (in male and female adults) within 3 days following a downshift in oxygen concentration from 0.2 to 0.1 mM in the culture medium. 3 days after downshift (2 days after in vivo incorporation of radiolabelled leucine), the β-homodimer contained 10–20% of the radiolabel in the three hemoglobins although β2 was usually not detectable in the protein stain of an overloaded gel. The amount of radioactive leucine incorporated per unit amount of protein was more than 300-times greater in the β2 homodimer than in the β-subunit of the heterodimer, suggesting that β2 does not dissociate rapidly during electrophoresis on the first dimension non-denaturing gel. This evidence for stable association of the two β-monomers and the 5–8 heme-binding domains within each monomer (in vivo and during electrophoresis on non-denaturing gels) allows us to exclude one of two alternative interpretations of genetic data published previously. We present an independent line of evidence for the dimer model of the native hemoglobins (which states that each polypeptide has many heme-binding domains). 相似文献
16.
There is evidence that glycans carrying terminal galactose residues are differently expressed in the sarcoplasm of different muscle fiber types. In this study monoclonal antibodies directed against P blood group antigens Pk: Galα1–4Galβ1–4Glcβ- and P1: Galα1–4Galβ1–4GlcNAcβ- were used to detect terminal α-galactosylated glycoconjugates on muscle proteins. Electrotransfer of proteins, extracted from human masseter and biceps muscles, to nitrocellulose after polyacrylamide gel electrophoresis (PAGE) and incubation with anti-Pk (CD77) consistently showed two bands with apparent molecular weights of 66 kDa and 64 kDa. In fresh frozen muscle sections from some humans there was endothelial reaction with anti-CD77 in capillaries, venules and veins but not in arterioles and arteries. In muscle samples from other humans there was no staining of endothelial cells. Formalin-fixed human muscle displayed a CD77 reaction with highest accumulation of reaction product at the periphery of the fibers. This may be explained by the presence of Pk glycoconjugates on intermediate filaments in muscle fibers. In preparations of cat masseter muscle proteins the antibodies against P1Pk antigens reacted with a 170 kDa and a 55 kDa band while in preparations of cat biceps brachii only a 55 kDa band was reactive. The specificities of the antibodies were investigated by fluorescence-activated cell sorter (FACS), α- and β-galactosidase digestion and inhibitory sugars. This study indicates that glycans carrying Galα1–4Galβ1- epitopes are expressed on myofibrillar associated proteins. 相似文献
17.
《Biochimica et Biophysica Acta (BBA)/General Subjects》2001,1568(1):60-66
The effect of α- and β-thymosin peptides, namely prothymosin α (ProTα), thymosin α1 (Tα1), parathymosin α (ParaTα), thymosin β4 (Tβ4), thymosin β10 (Tβ10), and thymosin β9 (Tβ9), on the angiogenesis process was investigated using the chick chorioallantoic membrane as an in vivo angiogenesis model. The thymosin peptides tested were applied in 10 μl aliquots containing 0.01–4 nmoles of Tβ4, Tβ10 or Tβ9, 0.016–6.66 nmoles of Tα1, 4.1 pmoles–1.66 nmoles of ProTα, and 4.4 pmoles–1.76 nmoles of ParaTα. Phorbol 12-myristate 13-acetate and hydrocortisone were also used as positive and negative control, respectively. Tβ4, ProTα and Tα1 were found to enhance angiogenesis, while Tβ10, Tβ9 and ParaTα exhibited an inhibitory effect on the angiogenesis process. When mixtures of Tβ4 and Tβ10 containing active amounts of the two peptides at different proportions were applied, the promoting effect of Tβ4 on angiogenesis was reversed in the presence of increasing concentrations of Tβ10 and vice versa. The effect of Tβ10, Tβ9, ProTα and ParaTα, in parallel with Tβ4 and Tα1, on the angiogenesis process was investigated for the first time as far as we know and the results of this study offer more insight into the biological regulatory roles of thymosin peptides, and provide helpful information about their therapeutic potential. Whether these agents could be used either as inhibitors of angiogenesis in disease states where uncontrolled angiogenesis is involved, e.g. in carcinogenesis, or as angiogenesis promoters that could be useful in wound healing, fracture repair, peptic ulcers etc., remains to be further studied. 相似文献
18.
Jie Shi Jie Wang Lu Yu Li Yang Shujuan Zhao Zhengtao Wang 《Journal of industrial microbiology & biotechnology》2017,44(7):1073-1082
Bear bile powder is a precious medicinal material. It is characterized by high content of tauroursodeoxycholic acid (TUDCA) at a ratio of 1.0–1.5 to taurochenodeoxycholic acid (TCDCA). Here, we reported the biotransformation of tauroursodeoxycholic acid (TUDCA) through Escherichia coli engineered with a two-step mimic biosynthetic pathway of TUDCA from taurochenodeoxycholic acid (TCDCA). Two 7α-hydroxysteroid dehydrogenase (7α-HSDH) and two 7β-hydroxysteroid dehydrogenase (7β-HSDH) genes (named as α1, α2, β1, and β2) were selected and synthesized to create four pathway variants using ePathBrick. All could convert TCDCA to TUDCA and the one harboring α1 and β2 (pα1β2) showed the strongest capability. Utilizing the oxidative and reductive properties of 7α- and 7β-HSDH, an ideal balance between TUDCA and TCDCA was established by optimizing the fermentation conditions. By applying the optimal condition, E. coli containing pα1β2 (BL-pα1β2) produced up to 1.61 ± 0.13 g/L of TUDCA from 3.23 g/L of TCDCA at a ratio of 1.3 to TCDCA. This study provides a potential approach for bear bile substitute production from cheap and readily available chicken bile. 相似文献
19.
Tsuguo Mizuochi Akira Kobata 《Biochemical and biophysical research communications》1980,97(2):772-778
Human chorionic gonadotropin (hCG) purified from placenta, like urinary hCG, is shown to have the sialylated forms of three neutral oligosaccharides: Galβ1→4GlcNAcβ1→2Manα1→6(Galβ1→4GlcNAcβ1→2Manα1→3)Manβ1→4GlcNAcβ1→4(Fucα1→6)GlcNAc (N-1), Galβ1→4GlcNAcβ1→2Manα1→6(Galβ1→4GlcNAcβ1→2Manα1→3)Manβ1→4GlcNAcβ1→4GlcNAc (N-2) and Manα1→6(Galβ1→4GlcNAcβ1→2Manα1→3)Manβ1→4GlcNAcβ1→4GlcNAc (N-3). Gel permeation chromatographic analysis of oligosaccharides released from α- and β-subunits of placental hCG has revealed that the α-subunit has one each of sialylated N-2 and N-3, while the β-subunit has one each of sialylated N-1 and N-2. 相似文献
20.
Channel functions of the neuronal α4β2 nicotinic acetylcholine receptor (nAChR), one of the most widely expressed subtypes in the brain, can be inhibited by volatile anesthetics. Our Na+ flux experiments confirmed that the second transmembrane domains (TM2) of α4 and β2 in 2:3 stoichiometry, (α4)2(β2)3, could form pentameric channels, whereas the α4 TM2 alone could not. The structure, topology, and dynamics of the α4 TM2 and (α4)2(β2)3 TM2 in magnetically aligned phospholipid bicelles were investigated using solid-state NMR spectroscopy in the absence and presence of halothane and isoflurane, two clinically used volatile anesthetics. 2H NMR demonstrated that anesthetics increased lipid conformational heterogeneity. Such anesthetic effects on lipids became more profound in the presence of transmembrane proteins. PISEMA experiments on the selectively 15N-labeled α4 TM2 showed that the TM2 formed transmembrane helices with tilt angles of 12° ± 1° and 16° ± 1° relative to the bicelle normal for the α4 and (α4)2(β2)3 samples, respectively. Anesthetics changed the tilt angle of the α4 TM2 from 12° ± 1° to 14° ± 1°, but had only a subtle effect on the tilt angle of the (α4)2(β2)3 TM2. A small degree of wobbling motion of the helix axis occurred in the (α4)2(β2)3 TM2. In addition, a subset of the (α4)2(β2)3 TM2 exhibited counterclockwise rotational motion around the helix axis on a time scale slower than 10- 4 s in the presence of anesthetics. Both helical tilting and rotational motions have been identified computationally as critical elements for ion channel functions. This study suggested that anesthetics could alter these motions to modulate channel functions. 相似文献