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951.
952.
酶分子在长期进化过程中形成一系列氨基酸残基组成的活性架构,参与底物的识别、结合与催化过程,而活性架构中相应氨基酸残基是如何影响酶分子结合底物的能力,进而影响酶分子的催化效率,一直是酶分子理性改造研究的热点.利用亲和电泳技术,可以快速展示内切纤维素酶Tr Cel12A和木聚糖酶Tl Xyn A活性架构中不同突变体的催化活性及其迁移率的变化,进而通过在不同底物浓度凝胶中蛋白质相对迁移率变化程度的定量回归分析,发现由氨基酸单点突变导致蛋白质迁移率的相对变化,可以定量表征酶分子突变前后结合底物能力的变化.亲和电泳测定的有效阻滞常数Kb值与等温滴定量热法和荧光光谱法测定的相关参数比较具有明显相关性.由于亲和电泳技术在测定酶分子与底物的结合能力时具有简便、快速、灵敏的特点,因而可作为常规生化实验室常规普筛技术来检测突变文库中系列突变体导致结合力的变化. 相似文献
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Despite numerous endometrial cancer cell lines, little is know about the progression and transition of primary cultured endometrial tumours. Herein, a stage I grade III endometrial adenocarcinoma was maintained in primary culture and the phenotypic and protein expression changes were observed in relation to passage number. At early passage numbers, cultured human endometrial cancer (CHEC) cells displayed classic epithelial cell morphology, growing in groups in a glandular structure and staining positive for cytokeratin. However, with increasing passage number, CHEC cells changed in morphology to display a stromal phenotype which was accompanied by a significant reduction in cytokeratin and increases in alpha-actin and vimentin expression. Simultaneous culture of stromal cells isolated from the original tumour failed to show the same morphological characteristics or protein expression patterns. We further characterised CHEC cells through a screening of cancer related proteins, among others, caveolin-1 and Tissue factor in comparison with established cancer cell lines and corresponding non-cancerous cells. This report demonstrates that endometrial adenocarcinoma cells in culture can undergo phenotypic and protein expression changes reminiscent of epithelial-mesenchymal transition. This work suggests that primary tumours and cell lines displaying stromal morphologies may have undergone epithelial-mesenchymal transition from an adenocarcinoma origin. 相似文献
956.
N-terminal sequence analysis of atrial granule serine proteinase purified by affinity chromatography
Atrial granule serine proteinase is considered the leading candidate endoproteolytic processing enzyme of pro-atrial natriuretic factor. Its cleavage specificity is directed toward a monobasic amino acid processing site, and as such, the atrial enzyme is distinguished from the family of prohormone convertases which act at dibasic amino acid processing sites. To delineate the molecular mechanisms which distinguish monobasic from dibasic amino acid-directed processing enzymes, pure atrial enzyme is needed for sequence determination leading to molecular cloning, and for preparation of antisera. An affinity chromatography purification scheme seemed a logical modification of our established procedures to yield suitable amounts of enzyme for further studies. Surprisingly, pseudo-peptide bond inhibitors of the atrial enzyme [Damodaran and Harris (1995),J. Protein Chem., this issue] formed ineffective affinity ligands, even though these compounds contain essential residues on either side of what would be the scissile bond in a peptide substrate. On the other hand, tripeptide aldehydes (based on the substrate recognition sequence of the atrial enzyme) linked to Sepharose formed effective affinity matrices, permitting purification of the enzyme in a single step from a subcellular fraction enriched for atrial granules and lysosomes. Hence, the enzyme was purified 2000-fold in 90% overall yield, and subjected to N-terminal sequence analysis through 26 residues. The sequence determined, XXPEAAGLPG[R, L]GNPVP[F, G]R[Q, I]XY[G, E]XR(N, A]V, indicates that the atrial enzyme is unique, showing little sequence homology to other proteins in the database.Abbreviations AGSP
atrial granule serine proteinase
- ANF
atrial natriuretic factor
- BSA
bovine serum albumin
-
Bz
benzoyl
- EACA
6()-aminocaproic acid
- HEPES
N-2-hydroxyethylpiperazine-N'-propanesulfonic acid
- HPLC
high-performance liquid chromatography
- PEG
polyethylene glycol-3350
- SDS-PAGE
sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Single-letter abbreviations are used to denote amino acids 相似文献
957.
Conserved signal transduction pathways that use phosphorelay from histidine kinases through an intermediate transfer protein (H2) to response regulators have been found in a variety of eukaryotic microorganisms. Several of these pathways are linked to mitogen-activated protein kinase cascades. These networks control different physiological responses including osmoregulation, cAMP levels and cellular morphogenesis. 相似文献
958.
Geethalakshmi Radhakrishnan Hironori Maeda Rajesh KatareGopalrao Hideaki Nishimori Eiji Toda Shiro Sasaguri 《Biochemical and biophysical research communications》2009,387(1):25-30
Dissolved organic matter (DOM) in seawater can be defined as the fraction of organic matter that passes through a filter of sub micron pore size. In this study, we have examined the effect of DOM of deep seawater (DSW) from Pacific Ocean on platelet aggregation and atherosclerosis progression. DSW was passed through a series of filters and then through an Octadecyl C18 filter; the retained substance in ethanol was designated as C18 extractable DOM (C18-DOM). Our studies showed that C18-DOM treatment inhibited platelet aggregation, P-selectin expression and activity of COX-1 significantly. C18-DOM increased the expression of anti-atherogenic molecule namely heme oxygenase-1 in endothelial cells and all these data showed that C18-DOM is exhibiting aspirin-like effects. Moreover our in vivo studies showed that C18-DOM feeding slowed remarkably the progression of atherosclerosis. Our study demonstrated a novel biological effect of oceanic DOM, which has several important implications, including a possible therapeutic strategy for atherosclerosis. 相似文献
959.
Dieke van Dinther Henrike Veninga Salvador Iborra Ellen G.F. Borg Leoni Hoogterp Katarzyna Olesek Marieke R. Beijer Sjoerd T.T. Schetters Hakan Kalay Juan J. Garcia-Vallejo Kees L. Franken Lamin B. Cham Karl S. Lang Yvette van Kooyk David Sancho Paul R. Crocker Joke M.M. den Haan 《Cell reports》2018,22(6):1484-1495
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