共查询到20条相似文献,搜索用时 15 毫秒
1.
Sonya Cressman Ying Sun E. Jane Maxwell Ning Fang David D. Y. Chen Pieter R. Cullis 《International journal of peptide research and therapeutics》2009,15(1):49-59
The cyclic peptide, cRGDf[N(me)]V, binds to the α
v
β
3 integrin and can disrupt binding of the integrin to its natural ligands in the extracellular matrix. In this work, the ability
of a water-soluble, fluorescently labeled variant of the RGD-containing peptide (cRGDfK-488) to bind to integrins on human
umbilical vascular endothelial cells (HUVEC) and subsequently undergo endocytosis was characterized. This information was
compared to the binding and uptake properties of an α
v
β
3 integrin-specific monoclonal antibody, LM609X. The specificity of the RGD-containing peptide is assessed by comparison with
control peptide that does not bind to the α
v
β
3 integrin, cRADfK-488. Using a high purity construct, it is shown that the RGD ligand exhibits dissociation constants in the
micromolar range whereas LM609X exhibits dissociation constants in the nanomolar range. However, the RGD ligand showed greater
uptake following incubation at temperatures which permit endocytosis. A 7.4-fold increase in uptake of the RGD peptide was
observed following a 1 h incubation with HUVEC at 37°C (an endocytosis permissive temperature), as compared to that at 4°C
(an endocytosis prohibitive temperature). In contrast, only a 1.9-fold increase in cell-associated fluorescence was observed
for similar incubations with LM609X. Results from fluorescence microscopy supports the notion that the RGD peptide is rapidly
endocytosed at 37°C as compared to LM609X. These results are discussed with regard to previous work indicating that RGD ligands
enter cells by integrin-independent pathways. These studies provide well-controlled measures of how RGD ligands stimulate
endocytosis. This may be of considerable interest for intracellular delivery of ligand-associated drugs in anti-angiogenic
applications. 相似文献
2.
Reichert J Grasnick D Afonin S Buerck J Wadhwani P Ulrich AS 《European biophysics journal : EBJ》2007,36(4-5):405-413
It is generally assumed that fusogenic peptides would require a certain conformation, which triggers or participates in the
rate-determining step of membrane fusion. Previous structure analyses of the viral fusion peptide from gp41 of HIV-1 have
yielded contradictory results, showing either an α-helical or a β-stranded conformation under different conditions. To find
out whether either of these conformations is relevant in the actual fusion process, we have placed sterically demanding substitutions
into the fusion peptide FP23 to prevent or partially inhibit folding and self-assembly. A single substitution of either D- or L-CF3-phenylglycine was introduced in different positions of the sequence, and the capability of these peptide analogues to fuse
large unilamellar vesicles was monitored by lipid mixing and dynamic light scattering. If fusion proceeds via a β-stranded
oligomer, then the D- and L-epimers are expected to differ systematically in their activity, since the D-epimers should be unable to form β-structures due to sterical hindrance. If an α-helical conformation is relevant for fusion,
then the D-epimers would be slightly disfavoured compared to the L-forms, hence a small systematic difference in fusion activity should be observed. Interestingly, we find that (1) all D- and L-epimers are fusogenically active, though to different extents compared to the wild type, and – most importantly – (ii) there
is no systematic preference for either the D- or L-forms. We therefore suggest that a well-structured α-helical peptide conformation or a β-stranded oligomeric assembly can
be excluded as the rate-determining state. Instead, fusion appears to involve conformationally disordered peptides with a
pronounced structural plasticity.
Dedicated to Prof. K. Arnold on the occasion of this 65th birthday. 相似文献
3.
Mylonas I Schiessl B Jeschke U Vogl J Makrigiannakis A Kuhn C Kunze S Schulze S Kainer F Friese K 《Journal of molecular histology》2006,37(1-2):43-52
During human pregnancy the placenta produces a variety of proteins like steroid hormones and their receptors that are responsible for the establishment and ongoing of the feto-placental unit. Inhibins are dimeric glycoproteins, composed of an α-subunit and one of two possible β-subunits (β
A or β
B). Aims of the present study were the determination of the frequency and tissue distribution patterns of the inhibin/activin subunits in human placental tissue of normal pregnancies and pregnancies complicated with fetal growth restriction (IUGR). Slides of paraffin embedded placental tissue were obtained after delivery from patients diagnosed with IUGR (n = 6) and normal term placentas (n = 8). Tissue samples were fixed and incubated with monoclonal antibodies inhibin/activin-subunits -α, -β
A, -β
B. Intensity of immunohistochemical reaction on the slides was analysed using a semi-quantitative score and statistical analysis was performed (P<0.05). A significant lower expression of the inhibin-α subunit in IUGR extravillous trophoblast compared to normal pregnancies was observed, while the inhibin-α immunostaining was significantly upregulated in syncytiotrophoblast. Additionally, a significant down-regulation of inhibin-β
B subunit in extravillous trophoblast cells in IUGR syncytiotrophoblast cells was demonstrated. A co-localisation of inhibin-α and the β-subunits was also observed, suggesting a production and secretion of intact inhibin A and inhibin B. Although the precise role of these inhibin/activin subunits in human placenta and IUGR pregnancies is still unclear, they could be involved in autocrine/paracrine signalling, contributing to several aspects like angiogenesis and tissue remodelling. 相似文献
4.
Eric Mossel Fernando Formaggio Giovanni Valle Marco Crisma Claudio Toniolo Mitsunobu Doi Toshimasa Ishida Quirinus B. Broxterman Johan Kamphuis 《International journal of peptide research and therapeutics》1998,5(2-3):223-225
Summary In order to obtain further information on the role played by phenyl ring position in the Cα-methylated α-amino acid side chain on peptide preferred conformation, the crystal-state structural preferences of Cα-methyl, Cα-phenylglycine peptides have been determined by X-ray diffraction. This study shows that either the fully extended conformation
or the β-bend/310-helical structures are adopted by peptides characterized by this Cα-methylated, β-branched, aromatic α-amino acid. 相似文献
5.
ZHU Pengcheng SANG Yingying XU Rener ZHAO Jing LI Changben ZHAO Shouyuan 《中国科学:生命科学英文版》2002,45(6):577-582
ADAM family consists of a number of transmembrane proteins that contain a disintegrin and metalloprotease domain. ADAMs are involved in a highly diverse set of biological processes, including fertilization, neurogenesis, myogenesis and inflammatory response. The ADAM proteins have both cell adhesion and protease activities. Adam22 is highly expressed in human brain. The adam22-/- mice presented severe ataxia and died before weaning, but the function of ADAM22 is still unknown. 14-3-3β interacting with ADAM22 was detected by using yeast two-hybrid assay. The specificity of interaction between ADAM22 and 14-3-3β was proved by in vitro binding assay and immunoprecipitation. The major 14-3-3β binding site was located in the last 28 amino acid residues of ADAM22 cytoplasmic tail. Protein 14-3-3β is abundant and plays an important role in mediating cell diffusion, migration and cell cycle control. The interaction of ADAM22 and 14-3-3β suggests that the ADAM22 may play a crucial role in neural function and development. 相似文献
6.
Alessandro Moretto Marta De Zotti Marco Crisma Fernando Formaggio Claudio Toniolo 《International journal of peptide research and therapeutics》2008,14(4):307-314
“Mono-N-methyl scan” is a rational approach for the optimization of the peptide biological properties. N-Methylation of the –CONH– functionality is also a useful tool for discriminating solvent exposed from intramolecularly H-bonded
secondary amide groups in peptides. We are currently extending this reaction to linear peptides based on Cα-tetrasubstituted α-amino acids. Following our study on the synthesis and conformation of the mono-N-methylated peptides from Cα-methylated residues, in this work we investigated the N-methylation reaction on homo-peptides to the pentamer level from the Cα-ethylated residue Cα,α-diethylglycine. Under the classical experimental conditions used, exclusively mono-N-methylation (on the N-terminal, acetylated residue) takes place, as unambiguously shown by mass spectrometry, 2D-NMR, and X-ray diffraction techniques.
This backbone modification does not seem to involve any significant change in the peptide conformation in the crystalline
state.
Dedicated to the memory of Prof. Miroslav T. Leplawy (Technical University of Łodz, Poland), who performed the first synthesis
of the extremely sterically demanding Cα,α-diethylglycine peptides. 相似文献
7.
A truncated mutant α-amylase, Xa-S2, was obtained from Xanthomonas campestris wild type α-amylases (Xa-WT) through random mutagenesis that contained 167 amino acid residues (approx 65% shorter than that
of Xa-WT). Secondary structure prediction implied that Xa-S2, would be unable to form the whole (β/α)8-barrel catalytic domain and did not have the three conserved catalytic residues of wild type α-amylase, but it still displays
the starch-hydrolyzing activity. Xa-S2 was prepared, characterized and compared to the recombinant wild-type enzymes. The
K
m for starch was 32 mg/ml; activity was optimal at pH 6.2 and 30°C. In contrast, the K
m for starch of Xa-WT was 8 mg/ml and optimal enzyme activity was at pH 6.0–6.2 and 45–50°C. Our results suggested that Xa-S2
is a new amylase with a minimal catalytic domain for hydrolyzing substrates with of α-1,4-glucosidic bonds.
T. Ke and X. D. Ma contributed equally to this work 相似文献
8.
Katherine E. S. Locock Graham A. R. Johnston Robin D. Allan 《Neurochemical research》2009,34(10):1698-1703
The incorporation of extra binding groups onto known ligands is a powerful tool for the development of more potent and selective
agents at target sites such as the GABA receptors. In the present work we have attempted to build on the activity of the know
potent GABAA agonist 4-ACP-3-CA and its cis and trans saturated analogues CACP and TACP. We have investigated reactions to add thiol substituents to the α,β-unsaturated system
of 4-ACP-3-CA. The reaction was successful with a limited number of thiols but gave products of mixed stereochemistry. The
resultant thioether amino acids were screened for activity at human recombinant α1β2 γ2L GABAA receptors. The most interesting derivative was the benzylthioether which acted as an antagonist with an IC50 of 42 μM for the inhibition of a GABA EC50 dose (50 μM). This study has shown that GABA analogues derived by thiol addition to 4-aminocyclopent-1-enecarboxylic acid display interesting antagonist activity at the α1β2γ2L GABAA receptor.
Special issue article in honour of Dr. Graham Johnston. 相似文献
9.
V. S. Ananthanarayanan S. K. Attah-poku P. L. Mukkamala P. H. Rehse 《Journal of biosciences》1985,8(1-2):209-221
We report here two sets of results on proline-containing linear peptides, one of which brings out the role of theβ-turn conformation in the structure of nascent collagen while the other points to the functional importance of the β-turn
in calcium-binding proteins. Based on the data on peptides containing the -Pro-Gly-sequence, we had proposed and experimentally
verified that theβ-turn conformation in these peptides is a structural requirement for the enzymic hydroxylation of the proline residues in
the nascent (unhydroxylated) procollagen molecule. Our recent data, presented here, on the conformation of peptides containing
both the -Pro-Gly- and -Gly-Pro-sequences reveal that while theβ-turn in the substrate molecule is required at the catalytic site of prolyl hydroxylase, the polyproline-II structure is necessary
for effective binding at the active site of the enzyme. Thus, peptides containing either theβ-turn or the polyproline-II structure alone are found to act only as inhibitors while those with the polyproline-II followed
byβ-turn serve as substrates of the enzyme. In another study, we have synthesized the two linear peptides: Boc-Pro-D-Ala-Ala-NHCH3 and Boc-Pro-Gly-Ala-NHCH3 each of which adopts, in solution, a structure with two consecutiveβ-turns, as judged from circular dichroism, infrared and nuclear magnetic resonance data. Drastic spectral changes are seen
in these peptides on binding to Ca2+. Both the peptides show a distinct specificity to Ca2+ over Mg2+, Na+ and Li+. A conformational change in the peptides occurs on Ca2+ binding which brings together the carbonyl groups to coordinate with the metal ion. These results imply a functional role
for theβ-turn in Ca2+ — binding proteins. 相似文献
10.
Integrins, a family of transmembrane heterodimeric polypeptides, mediate various biological responses including cell adhesion
and migration. In this report, we show that sphingosine-1-phosphate (S1P) activates integrin αvβ3 in endothelial cells (ECs) via the sphingosine-1-phosphate receptor subtype 1 (S1P1)-mediated signaling pathway. S1P treatment
results in the activation of integrin αvβ3 in the lamellipodia region of ECs, suggesting that integrin αvβ3 plays a critical role in the S1P-stimulated chemotactic response of ECs. Indeed, S1P treatment induces the association of
focal adhesion kinase (FAK) and cytoskeletal proteins with integrin αvβ3, the ligation of αv and β3 subunits, as well as enhances endothelial migration on vitronectin-coated substrata. Knockdown endothelial S1P1 receptor,
treatments with pertussis toxin or dominant-negative-Rho family GTPases abrogates the S1P-induced integrin αvβ3 activation in ECs. Consequently, these treatments markedly inhibit the S1P-induced endothelial migratory response on vitronectin-coated
substrata. Collectively, these data indicate that the S1P-mediated signaling via the S1P1/Gi/Rho GTPases pathway activates integrin αvβ3, which is indispensable for S1P-stimulated chemotactic response of ECs. 相似文献
11.
F. A. Carvalho J. P. Lopes de Almeida T. Freitas-Santos C. Saldanha 《The Journal of membrane biology》2009,228(2):89-97
Circulating acetylcholine, substrate of membrane acetylcholinesterase (AChE), is known to enhance the band 3 protein degree
of phosphorylation. The purpose of this study was to verify whether the band 3 phosphorylation status is associated with a
G protein and whether it is an influent factor on AChE enzyme activity. From blood samples of healthy donors, erythrocyte
suspensions were prepared and incubated with AChE substrate (acetylcholine) and inhibitor (velnacrine), along with protein
tyrosine kinase (PTK) and tyrosine phosphatase (PTP) inhibitors. AChE activity was determined by spectrophotometry and extract
samples were analyzed by western blotting using primary antibodies to different G protein subunits. Our results with phosphorylated
band 3 (PTP inhibitor) show an increase in erythrocyte AChE (p < 0.0001). A dephosphorylated band 3 state (PTK inhibitor) shows a significant decrease. We identified a potential linkage
of protein subunits Gαi1/2 and Gβ with band 3 protein. Gαi1/2 and Gβ may be linked to the band 3 C-terminal site. Gαi1/2 is associated with the band 3 N-terminal domain, except for the control and ACh aliquots. Gβ is associated with both phosphorylated and dephosphorylated band 3 in the presence of velnacrine. We conclude that an erythrocyte
G protein with subunits Gαi1/2 and Gβ is associated with band 3. AChE depends on the degree of band 3 phosphorylation and its association with Gαi1/2 and Gβ. 相似文献
12.
Aimed at achieving a good understanding of the 3-dimensional structures of human α1A-adrenoceptor (α1A-AR), we have successfully developed its homology model based on the crystal structure of β2-AR. Subsequent structural refinements were performed to mimic the receptor’s natural membrane environment by using molecular
mechanics (MM) and molecular dynamics (MD) simulations in the GBSW implicit membrane model. Through molecular docking and
further simulations, possible binding modes of subtype-selective α1A-AR antagonists, Silodosin, RWJ-69736 and (+)SNAP-7915, were examined. Results of the modeling and docking studies are qualitatively
consistent with available experimental data from mutagenesis studies. The homology model built should be very useful for designing
more potent subtype-selective α1A-AR antagonists and for guiding further mutagenesis studies.
Figure The superposition of β2-AR crystal structure (gold ribbons) and α1A-AR homology model (blue ribbons) 相似文献
13.
Kyoung-Soon Jang Woo-Jae Chung Hyun-Ki Kim Yun-Gon Kim Yoon-Sik Lee Byung-Gee Kim 《Biotechnology and Bioprocess Engineering》2008,13(4):445-452
A novel α-Gal resin was chemo-enzymatically synthesized for the efficient adsorption of anti-α-Gal antibodies in human serum
for xenotransplantation. To covalently conjugate a hexanoate linker with lactose and N-acetylglucosamine, both acceptor sugars were acetylated and brominated. Then, α-and β-galactoses were sequentially added
to the linker-containing saccharides at their non-reducing ends by using recombinant α-(1,3)-and β-(1,4)-galactosyltransferases
from E. coli. Finally, the synthesized α-Gal derivatives were immobilized on HiCore, a core-shell type resin, that was functionalized with amino groups on the shell region, as a packing material on-column.
Using this method we were able to demonstrate that the α-Gal HiCore resin had a reduced level of non-specific protein adsorption compared with the commercially available polystyrene supports,
TentaGel, and agarose-based supports, when Lectin BS-I was used as the model binding protein. Furthermore, the α-Gal HiCore resin was more efficient at eliminating anti-α-Gal IgGs from the total human IgGs through immunoadsorption than the other
two α-Gal resins, α-Gal TentaGel and α-Gal agarose. The α-Gal HiCore resin developed in this study can be utilized in a wide range of applications including ex vivo immunoadsorption and as a quantitative assay of anti-Gal antibody in human sera. 相似文献
14.
Amyloidogenic proteins (Aβ peptide) in Alzheimer’s disease (AD) and alpha-synuclein (α-Syn) in Parkinson’s disease (PD) are typically soluble monomeric
precursors, which undergo remarkable conformational changes and culminate in the form of aggregates in diseased condition.
Overlap of clinical and neuropathological features of both AD and PD are observed in dementia with Lewy body (DLB) disease,
the second most common form of dementia after AD. The identification of a 35-amino acid fragment of α-Syn in the amyloid plaques
in DLB brain have raised the possibility that Aβ and α-Syn interact with each other. In this report, the molecular interaction of α-Syn with Aβ40 and/or Aβ42 are investigated using multidimensional NMR spectroscopy. NMR data in the membrane mimic environment indicate specific
sites of interaction between membrane-bound α-Syn with Aβ peptide and vice versa. These Aβ–α-Syn interactions are demonstrated by reduced amide peak intensity or change in chemical shift of amide proton of the interacting
proteins. Based on NMR results, the plausible molecular mechanism of overlapping pathocascade of AD and PD in DLB due to interactions
between α-Syn and Aβ is described. To the best of our knowledge, it is the first report using multidimensional NMR spectroscopy that elucidates
molecular interactions between Aβ and α-Syn which may lead to onset of DLB.
An erratum to this article can be found at 相似文献
15.
Lia Millucci Roberto Raggiaschi Davide Franceschini Georg Terstappen Annalisa Santucci 《Journal of biosciences》2009,34(2):293-303
The highly toxic Aβ(25–35) is a peculiar peptide that differs from all the other commonly studied β-amyloid peptides because of its extremely rapid aggregation properties and enhanced neurotoxicity. We investigated Aβ(25–35) aggregation in H2O at pH 3.0 and at pH 7.4 by means of in-solution analyses. Adopting UV spectroscopy, Congo red spectrophotometry and thioflavin
T fluorimetry, we were able to quantify, in water, the very fast assembling time necessary for Aβ(25–35) to form stable insoluble aggregates and their ability to seed or not seed fibril growth. Our quantitative results,
which confirm a very rapid assembly leading to stable insoluble aggregates of Aβ(25–35) only when incubated at pH 7.4, might be helpful for designing novel aggregation inhibitors and to shed light on the
in vivo environment in which fibril formation takes place. 相似文献
16.
Atkins N Jones SM Guillette LJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2006,176(8):783-792
The southern snow skink Niveoscincus microlepidotus is a viviparous alpine lizard with biennial reproduction, in which embryos are fully developed before winter but parturition is delayed until spring. We aimed to determine whether, in this species, in vitro uterine preparations are responsive to arginine vasotocin (AVT) and prostaglandin (PGF2α) in autumn and spring, and whether pre-treatment with the β-adrenergic agonist isoproterenol decreases the effectiveness of AVT in stimulating uterine contractions. Using the spotted snow skink (Niveoscincus ocellatus), an annually breeding species, we aimed to determine influences of temperature and the β-adrenergic system upon the response to AVT in vivo. In both N. microlepidotus and N. ocellatus females are more responsive to AVT than to PGF2α, and that the response to AVT is decreased, but not prevented, by β-adrenergic stimulation. In N. microlepidotus, uteri are equally responsive in both seasons to the hormones administered. In N. ocellatus environmental conditions, specifically, temperature, modulate the response to AVT in vivo with the time to parturition increasing as temperature decreases. We conclude that in these viviparous squamates the endocrine cascade leading to parturition is modulated by the β-adrenergic system, and that this may reflect the mechanism by which the timing of parturition is tied to suitable environmental conditions. 相似文献
17.
Barbara Chan Panayotis Kalabalikis Nigel Klein Robert Heyderman Michael Levin 《Biotherapy》1996,9(4):221-228
A wide range of immunomodulating agents are now available which may be of benefit in reducing inflammatory cell activation
in meningococcal sepsis. In order to facilitate selection of candidate anti-inflammatory agents for clinical trials, we have
used an in vitro whole blood model to evaluate the effects on meningococcal induced neutrophil and monocyte activation, of
dexamethasone, prostacyclin, pentoxifylline and a human IgM anti-lipid A monoclonal antibody (HA-1A).
Known concentrations of heat and penicillin killed meningococci were added to whole blood and the time course of cellular
activation was determined. Using elastase-α
1-antitrypsin (elastase-α
1-AT) and TNFα production as markers of neutrophil and monocyte activation respectively, plasma levels of elastase-α
1-AT and TNFα were found to increase in a dose-dependant manner. Elastase-α
1-AT was detected early, with most release occurring between 15–30 min whereas TNFα was detected later, between 120–180 min.
Dexamethasone, prostacyclin and pentoxifylline caused a dose dependant inhibition of TNFα release but had no effect on elastase release. HA-1A had no effect on either TNFα or elastase release.
This model may be useful in determining the sequence of inflammatory cell activation and in selecting candidate anti-inflammatory
agents for evaluation in clinical trials. 相似文献
18.
The recombinant β-carotene 15,15′-monooxygenase from chicken liver was purified as a single 60 kDa band by His-Trap HP and Resource Q chromatography.
It had a molecular mass of 240 kDa by gel filtration indicating the native form to be tetramer. The enzyme converted β-carotene under maximal conditions (pH 8.0 and 37°C) with a k
cat of 1.65 min−1 and a K
m of 26 μM and its conversion yield of β-carotene to retinal was 120% (mol mol−1). The enzyme displayed catalytic efficiency and conversion yield for β-carotene, β-cryptoxanthin, β-apo-8′-carotenal, β-apo-4′-carotenal, α-carotene and γ-carotene in decreasing order but not for zeaxanthin, lutein, β-apo-12′-carotenal and lycopene, suggesting that the presence of one unsubstituted β-ionone ring in a substrate with a molecular weight greater than C30 seems to be essential for enzyme activity. 相似文献
19.
Summary. A procedure for the synthesis of enantiopure β3-amino acids from proteinogenic α-amino acids, developed by our group a few years ago, has been modified to enable the production
of C-2 fully deuterated, C-protected β3-amino acids and, even more important, the synthesis of valuable deuterium labelled N(Boc)-protected chiral synthons, such as 2-aminoalcohols, 2-aminoiodides, and β3-amino nitriles. 相似文献
20.
The amino acid sequences of 22 α-amylases from family 13 of glycosyl hydrolases were analyzed with the aim of revealing the
evolutionary relationships between the archaeal α-amylases and their eubacterial and eukaryotic counterparts. Two evolutionary
distance trees were constructed: (i) the first one based on the alignment of extracted best-conserved sequence regions (58
residues) comprising β2, β3, β4, β5, β7, and β8 strand segments of the catalytic (α/β)8-barrel and a short conserved stretch in domain B protruding out of the barrel in the β3 →α3 loop, and (ii) the second one
based on the alignment of the substantial continuous part of the (α/β)8-barrel involving the entire domain B (consensus length: 386 residues). With regard to archaeal α-amylases, both trees compared
brought, in fact, the same results; i.e., all family 13 α-amylases from domain Archaea were clustered with barley pI isozymes,
which represent all plant α-amylases. The enzymes from Bacillus licheniformis and Escherichia coli, representing liquefying and cytoplasmic α-amylases, respectively, seem to be the further closest relatives to archaeal α-amylases.
This evolutionary relatedness clearly reflects the discussed similarities in the amino acid sequences of these α-amylases,
especially in the best-conserved sequence regions. Since the results for α-amylases belonging to all three domains (Eucarya,
Eubacteria, Archaea) offered by both evolutionary trees are very similar, it is proposed that the investigated conserved sequence
regions may indeed constitute the ``sequence fingerprints' of a given α-amylase.
Received: 3 June 1998 / Accepted: 20 August 1998 相似文献