排序方式: 共有40条查询结果,搜索用时 15 毫秒
1.
M2 delta, a candidate for the structure lining the ionic channel of the nicotinic cholinergic receptor. 总被引:9,自引:2,他引:9
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
S Oiki W Danho V Madison M Montal 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(22):8703-8707
A synthetic 23-mer peptide that mimics the sequence of the putative transmembrane M2 segment of the Torpedo californica acetylcholine receptor (AcChoR) delta subunit--Glu-Lys-Met-Ser-Thr-Ala-Ile-Ser-Val-Leu-Leu-Ala-Gln-Ala-Val-Phe-Leu- Leu-Leu-Thr-Ser-Gln-Arg--forms discrete ionic channels in phosphatidylcholine bilayers. In contrast, a synthetic peptide that mimics the sequence of the putative M1 transmembrane segment of the Torpedo AcChoR delta subunit--Leu-Phe-Tyr-Val-Ile-Asn-Phe-Ile-Thr-Pro-Cys-Val-Leu-Ile-Ser-Phe- Leu-Ala-Ser-Leu-Ala-Phe-Tyr--does not form channels. The synthetic M2 delta channel peptide exhibits features that are characteristic of the authentic AcChoR channel, such as single channel conductances, discrimination of cations over anions, and channel lifetimes for open and closed states in the millisecond time range. Energetic considerations suggest that an aggregate of five amphipathic alpha-helices conforms the channel. Thus, the M2 segment may be a component of the AcChoR channel structure. 相似文献
2.
Synthetic peptides as substrates and inhibitors of a retroviral protease. 总被引:13,自引:2,他引:13
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
M Kotler R A Katz W Danho J Leis A M Skalka 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(12):4185-4189
Processing of the gag and pol gene precursor proteins of retroviruses is essential for infectivity and is directed by a viral protease that is itself included in one of these precursors. We demonstrate here that small synthetic peptides can be used as both model substrates and inhibitors to investigate the specificity and molecular parameters of the reaction. The results indicate that a peptide that extends five amino acids but not three amino acids in both directions from a known cleavage site is accurately hydrolyzed by the protease of avian sarcoma-leukosis virus. Substitutions of the amino acids to either side of the peptide bond to be cleaved affect the ability of the peptide (as well as a larger precursor protein) to serve as a substrate. The specificity is more stringent for the amino acid that will become the carboxyl end after cleavage. Some substitutions produced peptides that were not cleaved but could act as inhibitors of cleavage of a susceptible peptide. Thus, small model substrates may be used to explore both the binding and catalytic properties of these important proteases. 相似文献
3.
Koffi KG Sawadogo D Meite M Nanho DC Tanoh ES Attia AK Sanogo I Sangare A 《The hematology journal : the official journal of the European Haematology Association / EHA》2003,4(5):363-365
T-lymphocyte subsets were studied in two patient groups: (1) 50 patients with homozygous sickle cell anaemia (SCA) (mean age 12 (range 3-32) years old) in good health at the time of the study who showed no infectious complication. (2) 50 patients (mean age 13 (range 4-29) years old) with normal haemoglobin rate. The global response revealed a significant increase in levels of CD3+ (P=0.04) and CD8+ (P=0.04) cells when compared with the control group, there was no significant difference in levels of CD4+ cells (P=0.05) between the two groups. However, there was a relationship between T-cell subpopulation levels and spleen status. The average values of T-cell subsets (CD4+ and CD8+) in patients with SCA-induced splenic defects (asplenic, splenomegaly or splenectomized patients) were significantly reduced when compared to SCA patients with normal spleens and the control groups. These data show that T-cell activity was reduced in patients with splenic defects. A correlation between splenic status and a perturbed host defence system in patients with SCA suggests that monitoring T-cell subsets might have prognostic value in the course of sickle cell disease. 相似文献
4.
J Corre K Mahtouk M Attal M Gadelorge A Huynh S Fleury-Cappellesso C Danho P Laharrague B Klein T Rème P Bourin 《Leukemia》2007,21(5):1079-1088
Recent literature suggested that cells of the microenvironment of tumors could be abnormal as well. To address this hypothesis in multiple myeloma (MM), we studied bone marrow mesenchymal stem cells (BMMSCs), the only long-lived cells of the bone marrow microenvironment, by gene expression profiling and phenotypic and functional studies in three groups of individuals: patients with MM, patients with monoclonal gamopathy of undefined significance (MGUS) and healthy age-matched subjects. Gene expression profile independently classified the BMMSCs of these individuals in a normal and in an MM group. MGUS BMMSCs were interspersed between these two groups. Among the 145 distinct genes differentially expressed in MM and normal BMMSCs, 46% may account for a tumor-microenvironment cross-talk. Known soluble factors implicated in MM pathophysiologic features (i.e. IL (interleukin)-6, DKK1) were revealed and new ones were found which are involved in angiogenesis, osteogenic differentiation or tumor growth. In particular, GDF15 was found to induce dose-dependent growth of MOLP-6, a stromal cell-dependent myeloma cell line. Functionally, MM BMMSCs induced an overgrowth of MOLP-6, and their capacity to differentiate into an osteoblastic lineage was impaired. Thus, MM BMMSCs are abnormal and could create a very efficient niche to support the survival and proliferation of the myeloma cells. 相似文献
5.
D R Webb N Mensi J Freire-Moar H W Schnaper R V Lewis G Semenuk B H Devens A Koontz W Danho Y C Pan 《International immunology》1990,2(8):765-774
Soluble immune response suppressor (SIRS) is a low-molecular-weight protein (approximately 10,000 daltons) produced by mitogen- or interferon-activated T lymphocytes that can block development of humoral or cell-mediated immune responses in vivo or in vitro. As previously reported, murine SIRS is heterogeneous, eluting in two broad peaks on high performance reverse phase chromatography as well as displaying several broad isoelectric point forms. A putative N-terminal 21 amino acid sequence has been obtained for one of the less hydrophobic isoforms, SIRS-alpha 7. The sequence of SIRS-alpha 7 is unique in mammals but shows a remarkable homology to the family of short neurotoxins (short neurotoxin 1) found in sea snake, adder, and cobra species. A degenerate oligonucleotide probe based on the protein sequence was synthesized and was shown to hybridize to SIRS messenger RNA as measured by SIRS synthesis in a rabbit reticulocyte lysate system. A synthetic polypeptide based on the 21-residue sequence was also prepared and coupled to thyroglobulin or keyhole limpet hemocyanin. These were used to prepare rabbit antisera that neutralize SIRS bioactivity and precipitate authentic SIRS. 相似文献
6.
Intramolecular dislocation of the COOH terminus of the lac carrier protein in reconstituted proteoliposomes. 总被引:22,自引:11,他引:11
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
N Carrasco D Herzlinger R Mitchell S DeChiara W Danho T F Gabriel H R Kaback 《Proceedings of the National Academy of Sciences of the United States of America》1984,81(15):4672-4676
A dodecapeptide corresponding to the carboxyl terminus of the lac carrier of Escherichia coli was synthesized, coupled to thyroglobulin, and the conjugate was used to generate site-directed polyclonal antibodies. The antibodies react with the carboxyl-terminal peptide and with the lac carrier protein, while monoclonal antibody 4B1 reacts with intact lac carrier protein, but not with the carboxyl-terminal peptide. Antibody 4B1 binds preferentially to right-side-out membrane vesicles relative to inside-out vesicles, confirming the presence of the 4B1 epitope on the periplasmic surface of the membrane. Alternatively, anti-carboxyl-terminal antibody binds preferentially to inside-out vesicles, demonstrating that the carboxyl terminus of the lac carrier protein is on the cytoplasmic surface. Surprisingly, both antibodies bind to proteoliposomes reconstituted with purified lac carrier protein, and quantitative binding assays indicate that the epitopes are equally accessible. When proteoliposomes containing purified lac carrier protein are digested with carboxypeptidases A and B, binding of anti-carboxyl-terminal antibodies decreases by greater than 80%, while binding of antibody 4B1 and various transport activities remain essentially unchanged. It is suggested that during reconstitution, the lac carrier protein undergoes intramolecular dislocation of the carboxyl terminus with no significant effect on its catalytic activity. 相似文献
7.
Detection and quantification of human anti-Sm antibodies using synthetic peptide and recombinant SmB antigens 总被引:5,自引:0,他引:5
Anti-Sm-positive sera from patients with systemic lupus erythematosus (SLE) recognize a major epitope located within the carboxyl-terminal 27 amino acids of a recombinant SmB fusion protein. To determine whether a synthetic peptide corresponding to this region could be used as an antigen to detect anti-Sm antibodies, sera were typed as anti-Sm positive or anti-Sm negative by counterimmunoelectrophoresis (CIE). Twenty-three SLE sera that were anti-Sm positive by CIE, 22 that were anti-Sm negative by CIE, and 42 sera from patients with other autoimmune diseases were tested for anti-Sm antibodies by enzyme-linked immunosorbent assay (ELISA), using either the synthetic peptide (C27) or a recombinant SmB (rSmB) fusion protein as the antigen. More than 90% of the sera that were anti-Sm positive by CIE were also positive by both the C27 and rSmB ELISAs, and an additional 2 SLE sera originally typed as anti-Sm negative were found to be positive (1 by the C27 ELISA, 1 by the rSmB ELISA), due to the greater sensitivity of the ELISAs. In the rSmB ELISA, anti-Sm antibodies were not detected in any of the sera from patients with other autoimmune diseases, whereas 3 patients with anti-U1 RNP antibodies (1 each with polymyositis, scleroderma, and mixed connective tissue disease) had a positive result in the C27 ELISA. These results indicate that both the C27 synthetic peptide and rSmB are excellent antigens for use in ELISAs to quantify anti-Sm antibodies. 相似文献
8.
Channel protein engineering: synthetic 22-mer peptide from the primary structure of the voltage-sensitive sodium channel forms ionic channels in lipid bilayers. 总被引:5,自引:2,他引:5
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
S Oiki W Danho M Montal 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(7):2393-2397
A synthetic 22-mer peptide that mimics the sequence of a putative pore segment of the voltage-dependent sodium channel forms transmembrane ionic channels in lipid bilayers. Several features of the authentic sodium channel are exhibited by the synthetic peptide: (i) The single channel conductance of the most frequent event is 20 pS in 0.5 M NaCl. (ii) The single channel open and closed lifetimes are in the ms time range. (iii) The synthetic channel discriminates cations over anions but is nonselective between Na+ and K+. However, the synthetic channel displays no significant voltage dependence. Energetic considerations suggest a bundle of four parallel amphipathic alpha-helices as the most plausible channel structure. The synthetic 22-mer channel-forming peptide allows study of the mechanisms of ion permeation through sodium channels by protein engineering techniques. 相似文献
9.
Gustave Kouassi Koffi Aissata Tolo Danho Clotaire Nanho Emeraude N’dathz Mathias Yao Kouassi Fatou Diago N’Diaye Boidy Kouakou N’dogomo Meité Romeo Ayemou Mamadou Sekongo Paul Kouehion Mori Meité Norbert Dagnekpo Tea Amadou Sangaré Ibrahima Sanogo 《International journal of hematology》2010,91(5):838-843
African Burkitt lymphomas (BL) are highly aggressive lymphomas mainly affecting children and young adults in Africa. This lymphoma was marked by its high sensitivity to chemotherapy in comparison to Sporadic Burkitt lymphoma. In this study, we evaluated the treatment response and survival of patients with CMA protocol. Eighty-five of the 105 children registered were evaluated for response; there were 46 boys and 39 girls, whose age at diagnosis ranged from 3 to 18 years (median 11 years), admitted to the Hematology National Teaching Hospital of Abidjan in the period 1998–2008 with a diagnosis of BL on histological review and who were given CMA chemotherapy with curative intent are included in this analysis. CMA protocol is a low intermediate regimen of 3 drugs [Cytarabin (ara-C), Methotrexate (MTX), and Cyclophosphamide] with CNS-directed treatment by intrathecal MTX, ara-C and corticosteroid. Fifty-five of 85 patients obtained CR after induction therapy and 10 after 3 supplementary cycle because of partial response. The overall complete remission was 76%. Fifty-three of patients were alive in first CR at a median survival rate period of 2 years (range 82 days to 9 years) and are continuously disease free from Burkitt lymphomas. Twelve patients relapse after CR and died of lymphoma progression. More than 32 patients died, as a result of lymphoma progression. Among the 32 dead, 10 were in Murphy stage IV and all the patients who presented bone marrow involvement died. The projected 5-year overall survival rate was 62%. In conclusion, CMA protocol shows the high sensitivity of African Burkitt lymphoma. This can be considered as a successful result for people living in poor socio-economic conditions with no health insurance. 相似文献
10.
Abrogoua DP Dano DS Manda P Adepo AJ Kablan BJ Goze NB Ehoulé K 《Journal of ethnopharmacology》2012,141(3):840-847