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41.
D J Takemoto S A Kaplan M M Appleman 《Biochemical and biophysical research communications》1979,90(2):491-497
The cyclic adenosine 3′,5′-monophosphate (cyclic AMP) phosphodiesterase from human leukemic lymphocytes differes from the normal cell enzyme in having a much higher activity and a loss of inhibition by cyclic guanosine 3′,5′-monophosphate (cyclic GMP). In an effort to determine the mechanism of these alterations, we have studied this enzyme in a model system, lectin-stimulated normal human lymphocytes. Following stimulation of cells with concanavalin A (con A) the enzyme activity gradually becomes altered, until it fully resembles the phosphodiesterase found in leukemic lymphocytes. The changes in the enzyme parallel cell proliferation as measured by increases in thymidine incorporation into DNA. The addition of a guanylate cyclase inhibitor preparation from the bitter melon prevents both the changes in the phosphodiesterase and the thymidine incorporation into DNA. This blockage can be partially reversed by addition of 8-bromo cyclic guanosine 3′,5′-monophosphate (8-bromo cyclic GMP) to the con A-stimulated normal lymphocytes. These results indicate a possible role of cyclic GMP in a growth related alteration of cyclic AMP phosphodiesterase. 相似文献
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44.
家蚕神经肽基因的筛查及成熟肽的预测 总被引:1,自引:0,他引:1
神经肽(neuropeptide)是家蚕Bombyx mori体内重要的调控物质。为了充分理解神经肽对家蚕发育的调控, 扩充家蚕神经肽的数量, 本研究利用BLAST的tblastn程序结合OpenOffice软件的查找程序, 基于其他昆虫和无脊椎动物神经肽的同源性和保守的结构特点, 在家蚕基因、理论蛋白质数据库及NCBI中进行全面而系统的基因筛查; 并利用各种在线工具对所筛查到基因和理论蛋白质的结构和成熟肽进行预测分析。结果共获得allatostatin-A (AST-A), allatostatin-B (AST-B), allatostatin-C (AST-C), allatropin (AT), ecdysis-triggering hormone (ETH), crustacean cardioactive peptide (CCAP)和FMRFamide等31个神经肽基因家族, 包括37个神经肽基因亚家族, 共计44个神经肽基因; 预测出193个成熟的神经肽, 其中73个根据家族同源性预测在C末端发生酰胺化, 而6个被预测在N末端发生了环化, 9个被预测酪氨酸发生了硫酸化。大部分成熟神经肽都具有明显的家族结构特征, 但proctolin, CCAP及CAPA-PK成熟肽结构上与其他昆虫相比有所扩展。结果提示, 家蚕神经和内分泌细胞产生了几乎在所有昆虫中具有的神经肽前体; 进化过程中大部分成熟神经肽的氨基酸序列在种间产生了差异, 但家族特征性基序高度保守。本研究为神经肽功能研究以及神经肽对家蚕发育尤其是蛹期发育调控的研究奠定了基础。 相似文献
45.
Peter Hammershøj Mikkel Jessing Anders Ø. Madsen Knud J. Jensen Jørn B. Christensen Ulrik Boas 《International journal of peptide research and therapeutics》2007,13(1-2):209-212
The development of new linkers (handles) for solid-phase synthesis provides new chemical opportunities for peptide synthesis.
To understand the chemical properties of a recently developed backbone amide linker from a structural perspective, the crystal
structure of S-((5-formyl-3,4-ethylenedioxy)thiophene-2-yl)-3-thiopropionic acid (T-BAL2) was studied. Specifically, we wished
to address whether this highly substituted thiophene retained planarity in the aromatic ring as well as between the aromatic
ring and the aldehyde carbonyl. Furthermore, we sought an explanation for the relatively low reactivity in reductive aminations
of the thienylaldehyde with amines in solution and on solid phase. Based on the crystal structure of T-BAL2, the thienyl-C
(aldehyde) and C–O (aldehyde) bond lengths were applied as measures for the electron-deficiency (electrophilicity) of the
aldehyde and compared to similar bond lengths found in previously reported formylated homo- and hetero-aromatic systems, which
show significantly higher reactivity towards imine formation. The bond lengths found in the present structure are in accordance
with normal C–C single bond and C–O double bond lengths. The high similarity in aldehyde bond lengths in the present system
and in the reported systems indicates similar electron distribution in these systems. The lower reactivity of the present
system may therefore not be attributed to electronic factors. 相似文献
46.
HE Xiaolin LIU Xinqi ZENG Zonghao LI Hongmin WANG Miao ZHANG Ying WANG Dacheng 《中国科学C辑(英文版)》2000,43(1):39-46
BmK M4 is a neutral neurotoxin in the BmK toxin series.It is medially toxic and belongs to group III α-toxins.The purified sample was crystallized in rhombic space group P61.Using an X-ray diffraction technique,the crystal structure of BmK M4 was revealed by molecular replacement at 0.20 nm resolution.The model was refined.The final crystallographic R factor was 0.142 and the free R factor was 0.173.The root mean square deviation is 0.001 5 nm for the bond length and 1.753°for the bond angles.64 water molecules were added to the asymmetric unit.The refined structure showed an unusual non-prolyl cis peptide bond at residue 10.The structure was compared with group II α-toxin BmK M8 (an acidic,weak toxin).The potential structural implications of the cis peptide bond were discussed. 相似文献
47.
Preferred proline puckerings in cis andtrans peptide groups: Implications for collagen stability 下载免费PDF全文
Luigi Vitagliano Rita Berisio Antonio Mastrangelo Lelio Mazzarella Adriana Zagari 《Protein science : a publication of the Protein Society》2001,10(12):2627-2632
The interplay between side-chain and main-chain conformations is a distinctive characteristic of proline residues. Here we report the results of a statistical analysis of proline conformations using a large protein database. In particular, we found that proline residues with the preceding peptide bond in the cis state preferentially adopt a down puckering. Indeed, out of 178 cis proline residues, as many as 145 (81%) are down. By analyzing the 1-4 and 1-5 nonbonding distances between backbone atoms, we provide a structural explanation for the observed trend. The observed correlation between proline puckering and peptide bond conformation suggests a new mechanism to explain the reported shift of the cis-trans equilibrium in proline derivatives. The implications of these results for the current models of collagen stability are also discussed. 相似文献
48.
Peter S. Thuy-Boun Ana Y. Wang Ana Crissien-Martinez Janice H. Xu Sandip Chatterjee Gregory S. Stupp Andrew I. Su Walter J. Coyle Dennis W. Wolan 《Molecular & cellular proteomics : MCP》2022,21(3):100197
The gut microbiota plays an important yet incompletely understood role in the induction and propagation of ulcerative colitis (UC). Organism-level efforts to identify UC-associated microbes have revealed the importance of community structure, but less is known about the molecular effectors of disease. We performed 16S rRNA gene sequencing in parallel with label-free data-dependent LC-MS/MS proteomics to characterize the stool microbiomes of healthy (n = 8) and UC (n = 10) patients. Comparisons of taxonomic composition between techniques revealed major differences in community structure partially attributable to the additional detection of host, fungal, viral, and food peptides by metaproteomics. Differential expression analysis of metaproteomic data identified 176 significantly enriched protein groups between healthy and UC patients. Gene ontology analysis revealed several enriched functions with serine-type endopeptidase activity overrepresented in UC patients. Using a biotinylated fluorophosphonate probe and streptavidin-based enrichment, we show that serine endopeptidases are active in patient fecal samples and that additional putative serine hydrolases are detectable by this approach compared with unenriched profiling. Finally, as metaproteomic databases expand, they are expected to asymptotically approach completeness. Using ComPIL and de novo peptide sequencing, we estimate the size of the probable peptide space unidentified (“dark peptidome”) by our large database approach to establish a rough benchmark for database sufficiency. Despite high variability inherent in patient samples, our analysis yielded a catalog of differentially enriched proteins between healthy and UC fecal proteomes. This catalog provides a clinically relevant jumping-off point for further molecular-level studies aimed at identifying the microbial underpinnings of UC. 相似文献
49.
Jonathan W. Yewdell 《Molecular & cellular proteomics : MCP》2022,21(7):100230
In the 35 years since the revelation that short peptides bound to major histocompatibility complex class I and II molecules are the secret of the major histocompatibility complex–restricted nature of T-cell recognition, there has been enormous progress in characterizing the immunopeptidome, the repertoire of peptide presented for immunosurveillance. Here, the major milestones in the journey are marked, the contribution of proteasome-mediated splicing to the immunopeptidome is discussed, and exciting recent findings relating the immunopeptidome to the translatome revealed by ribosome profiling (RiboSeq) is detailed. Finally, what is needed for continued progress is opined about, which includes the infusion of talented young scientists into the antigen-processing field, currently undergoing a renaissance; thanks in part to the astounding success of T-cell–based cancer immunotherapy. 相似文献
50.