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排序方式: 共有125条查询结果,搜索用时 15 毫秒
1.
P Zhong S D Pratt R P Edalji K A Walter T F Holzman A G Shivakumar L Katz 《Journal of bacteriology》1995,177(15):4327-4332
ErmC' is a methyltransferase that confers resistance to the macrolide-lincosamide-streptogramin B group of antibiotics by catalyzing the methylation of 23S rRNA at a specific adenine residue (A-2085 in Bacillus subtilis; A-2058 in Escherichia coli). The gene for ErmC' was cloned and expressed to a high level in E. coli, and the protein was purified to virtual homogeneity. Studies of substrate requirements of ErmC' have shown that a 262-nucleotide RNA fragment within domain V of B. subtilis 23S rRNA can be utilized efficiently as a substrate for methylation at A-2085. Kinetic studies of the monomethylation reaction showed that the apparent Km of this 262-nucleotide RNA oligonucleotide was 26-fold greater than the value determined for full-size and domain V 23S rRNA. In addition, the Vmax for this fragment also rose sevenfold. A model of RNA-ErmC' interaction involving multiple binding sites is proposed from the kinetic data presented. 相似文献
2.
Shivakumar Pattada Devaiah Deborah Vicuna Requesens Yeun-Kyung Chang Kendall R. Hood Ashley Flory John A. Howard Elizabeth E. Hood 《Transgenic research》2013,22(3):477-488
The technology of converting lignocellulose to biofuels has advanced swiftly over the past few years, and enzymes are a significant constituent of this technology. In this regard, cost effective production of cellulases has been the focus of research for many years. One approach to reach cost targets of these enzymes involves the use of plants as bio-factories. The application of this technology to plant biomass conversion for biofuels and biobased products has the potential for significantly lowering the cost of these products due to lower enzyme production costs. Cel6A, one of the two cellobiohydrolases (CBH II) produced by Hypocrea jecorina, is an exoglucanase that cleaves primarily cellobiose units from the non-reducing end of cellulose microfibrils. In this work we describe the expression of Cel6A in maize endosperm as part of the process to lower the cost of this dominant enzyme for the bioconversion process. The enzyme is active on microcrystalline cellulose as exponential microbial growth was observed in the mixture of cellulose, cellulases, yeast and Cel6A, Cel7A (endoglucanase), and Cel5A (cellobiohydrolase I) expressed in maize seeds. We quantify the amount accumulated and the activity of the enzyme. Cel6A expressed in maize endosperm was purified to homogeneity and verified using peptide mass finger printing. 相似文献
3.
Kumaran C Shivakumar K 《American journal of physiology. Heart and circulatory physiology》2002,282(5):H1855-H1862
Substance P is released from nerve endings in the heart under pathological conditions like ischemia, but its action on cardiac cells has not been investigated. This study tested the hypothesis that substance P is mitogenic to adult cardiac fibroblasts and delineated the underlying mechanism(s). Substance P, acting via neurokinin-1 (NK-1) receptors, stimulated cellular hyperplasia over a range of 1-10 micromol/l. It elicited no change in net collagen production, total protein synthesis, or cell protein content but increased (45)Ca uptake and superoxide generation. EGTA, N-acetyl-cysteine, and superoxide dismutase attenuated the hyperplastic response to substance P. A combination of substance P and EGTA enhanced superoxide generation without an increase in DNA synthesis, showing that an increase in superoxide production does not result in hyperplasia when extracellular Ca(2+) is chelated. Together, the data suggest that substance P may activate, via NK-1 receptors, a hyperplastic but not hypertrophic response in adult cardiac fibroblasts and that alterations in redox state and Ca(2+) homeostasis may act in concert to mediate its mitogenic action. 相似文献
4.
Cerium (Ce), a rare earth element, has been postulated to play a role in the pathogenesis of tropical endomyocardial fibrosis (EMF). Investigations carried out recently in pursuance of the postulation furnished histological evidence of EMF and increased cardiac collagen content in rats on prolonged administration of Ce. The present study was undertaken to understand the molecular basis of myocardial injury and fibrosis produced by the element. This article presents evidence of increased lipid peroxidation and elevated rates of fibroblast proliferation and collagen deposition in the heart in Ce-treated rats. It is suggested that the element may trigger a wound-healing response in the cardiac tissue leading to cardiac fibrosis. 相似文献
5.
Samples from biogas digesters, sewage ponds, animal house effluents and food processing wastes were used in enrichment systems seeking anaerobic bacteria producing pectinases. Among the 46 anaerobic consortia developed from various samples, four showed high pectinase activity under static anaerobic conditions. Investigation of fermentation variables showed the optimum conditions for pectinase activity were pH 7.0, 45°C and 72 h of growth with 0.5% pectin in the cultivation medium. A 1.4- to 1.6-fold increase in the pectinase activity was achieved under these conditions. The maximum yield of enzymes (62.72 U ml-1 of pectinase, 4.74 U ml-1 of polygalacturonase, 113.30 U ml-1 of pectin lyase, 2.10 U ml-1 of pectinesterase, 0.75 U ml-1 of total cellulase and 9.27 U ml-1 of xylanase) was recorded with the consortia C-S2 developed from decomposed plant samples collected from a pond. 相似文献
6.
Arrestin‐Domain Containing Protein 1 (Arrdc1) Regulates the Protein Cargo and Release of Extracellular Vesicles 下载免费PDF全文
Sushma Anand Natalie Foot Ching‐Seng Ang Kelly M. Gembus Shivakumar Keerthikumar Christopher G. Adda Suresh Mathivanan Sharad Kumar 《Proteomics》2018,18(17)
Extracellular vesicles (EVs) are lipid‐bilayered vesicles that are released by multiple cell types and contain nucleic acids and proteins. Very little is known about how the cargo is packaged into EVs. Ubiquitination of proteins is a key posttranslational modification that regulates protein stability and trafficking to subcellular compartments including EVs. Recently, arrestin‐domain containing protein 1 (Arrdc1), an adaptor for the Nedd4 family of ubiquitin ligases, has been implicated in the release of ectosomes, a subtype of EV that buds from the plasma membrane. However, it is currently unknown whether Arrdc1 can regulate the release of exosomes, a class of EVs that are derived endocytically. Furthermore, it is unclear whether Arrdc1 can regulate the sorting of protein cargo into the EVs. Exosomes and ectosomes are isolated from mouse embryonic fibroblasts isolated from wild type and Arrdc1‐deficient (Arrdc1?/?) mice. Nanoparticle tracking analysis–based EV quantitation shows that Arrdc1 regulates the release of both exosomes and ectosomes. Proteomic analysis highlights the change in protein cargo in EVs upon deletion of Arrdc1. Functional enrichment analysis reveals the enrichment of mitochondrial proteins in ectosomes, while proteins implicated in apoptotic cleavage of cell adhesion proteins and formation of cornified envelope are significantly depleted in exosomes upon knockout of Arrdc1. 相似文献
7.
James E. Squires Pranavkumar Shivakumar Reena Mourya Kazuhiko Bessho Stephanie Walters Jorge A. Bezerra 《PloS one》2015,10(5)
ConclusionsLower inoculation of RRV-induced progressive liver injury and fibrosis via NK cells. These findings point to the potential use of NK cell-depleting strategies to block progression of liver disease in biliary atresia. 相似文献
8.
9.
Bharat Bhusan Majhi Guy Sobol Sarah Gachie Shivakumar Sreeramulu Guido Sessa 《Molecular Plant Pathology》2021,22(7):786-799
Pattern-triggered immunity (PTI) is typically initiated in plants by recognition of pathogen- or damage-associated molecular patterns (PAMP/DAMPs) by cell surface-localized pattern recognition receptors (PRRs). Here, we investigated the role in PTI of Arabidopsis thaliana brassinosteroid-signalling kinases 7 and 8 (BSK7 and BSK8), which are members of the receptor-like cytoplasmic kinase subfamily XII. BSK7 and BSK8 localized to the plant cell periphery and interacted in yeast and in planta with FLS2, but not with other PRRs. Consistent with a role in FLS2 signalling, bsk7 and bsk8 single and bsk7,8 double mutant plants were impaired in several immune responses induced by flg22, but not by other PAMP/DAMPs. These included resistance to Pseudomonas syringae and Botrytis cinerea, reactive oxygen species accumulation, callose deposition at the cell wall, and expression of the defence-related gene PR1, but not activation of MAP kinases and expression of the FRK1 and WRKY29 genes. bsk7, bsk8, and bsk7,8 plants also displayed enhanced susceptibility to P. syringae and B. cinerea. Finally, BSK7 and BSK8 variants mutated in their myristoylation site or in the ATP-binding site failed to complement defective phenotypes of the corresponding mutants, suggesting that localization to the cell periphery and kinase activity are critical for BSK7 and BSK8 functions. Together, these findings demonstrate that BSK7 and BSK8 play a role in PTI initiated by recognition of flg22 by interacting with the FLS2 immune receptor. 相似文献
10.
Sapna S Ranjith SK Shivakumar K 《American journal of physiology. Heart and circulatory physiology》2006,291(1):H436-H440
Mechanisms underlying cardiac fibrogenesis in magnesium deficiency are unclear. It was reported earlier from this laboratory that serum from magnesium-deficient rats has a more pronounced stimulatory effect on cell proliferation, net collagen production, and superoxide generation in adult rat cardiac fibroblasts than serum from rats on the control diet. The profibrotic serum factors were, however, not identified. This study tested the hypothesis that circulating angiotensin II may modulate cardiac fibroblast activity in hypomagnesemic rats. Male Sprague-Dawley rats were pair-fed a magnesium-deficient (0.0008% Mg) or -sufficient (0.05%) diet for 6 days, and the effects of serum from these rats on [3H]thymidine and [3H]proline incorporation into cardiac fibroblasts from young adult rats were evaluated in the presence of losartan, an angiotensin II type 1 (AT1) receptor antagonist, and spironolactone, an aldosterone antagonist. Losartan and spironolactone markedly attenuated the stimulatory effects in vitro of serum from the magnesium-deficient and control groups, but the inhibitory effects were considerably higher in cells exposed to serum from magnesium-deficient animals. Circulating and cardiac tissue levels of angiotensin II were significantly elevated in magnesium-deficient animals (67.6% and 93.1%, respectively, vs. control). Plasma renin activity was 61.9% higher in magnesium-deficient rats, but serum angiotensin-converting enzyme activity was comparable in the two groups. Furthermore, preliminary experiments in vivo using enalapril supported a role for angiotensin II in magnesium deficiency. There was no significant difference between the groups in serum aldosterone levels. The findings suggest that circulating angiotensin II and aldosterone may stimulate fibroblast activity and contribute to a fibrogenic response in the heart in magnesium deficiency. 相似文献