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排序方式: 共有1376条查询结果,搜索用时 171 毫秒
81.
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83.
Nomfundo Nzuza Tiara Padayachee Wanping Chen Dominik Gront David R. Nelson Khajamohiddin Syed 《Current issues in molecular biology》2021,43(3):1374
Ferredoxins, iron-sulfur (Fe-S) cluster proteins, play a key role in oxidoreduction reactions. To date, evolutionary analysis of these proteins across the domains of life have been confined to observing the abundance of Fe-S cluster types (2Fe-2S, 3Fe-4S, 4Fe-4S, 7Fe-8S (3Fe-4s and 4Fe-4S) and 2[4Fe-4S]) and the diversity of ferredoxins within these cluster types was not studied. To address this research gap, here we propose a subtype classification and nomenclature for ferredoxins based on the characteristic spacing between the cysteine amino acids of the Fe-S binding motif as a subtype signature to assess the diversity of ferredoxins across the living organisms. To test this hypothesis, comparative analysis of ferredoxins between bacterial groups, Alphaproteobacteria and Firmicutes and ferredoxins collected from species of different domains of life that are reported in the literature has been carried out. Ferredoxins were found to be highly diverse within their types. Large numbers of alphaproteobacterial species ferredoxin subtypes were found in Firmicutes species and the same ferredoxin subtypes across the species of Bacteria, Archaea, and Eukarya, suggesting shared common ancestral origin of ferredoxins between Archaea and Bacteria and lateral gene transfer of ferredoxins from prokaryotes (Archaea/Bacteria) to eukaryotes. This study opened new vistas for further analysis of diversity of ferredoxins in living organisms. 相似文献
84.
Tumors often harbor orders of magnitude more mutations than healthy tissues. The increased number of mutations may be due to an elevated mutation rate or frequent cell death and correspondingly rapid cell turnover, or a combination of the two. It is difficult to disentangle these two mechanisms based on widely available bulk sequencing data, where sequences from individual cells are intermixed and, thus, the cell lineage tree of the tumor cannot be resolved. Here we present a method that can simultaneously estimate the cell turnover rate and the rate of mutations from bulk sequencing data. Our method works by simulating tumor growth and finding the parameters with which the observed data can be reproduced with maximum likelihood. Applying this method to a real tumor sample, we find that both the mutation rate and the frequency of death may be high. 相似文献
85.
Knittel T Kobold D Piscaglia F Saile B Neubauer K Mehde M Timpl R Ramadori G 《Histochemistry and cell biology》1999,112(5):387-401
Previous in vitro studies indicated that hepatic stellate cells (HSC) and rat liver myofibroblasts (rMF) have to be regarded
as different cell populations of the myofibroblastic lineage with fibrogenic potential. Employing the discrimination features
defined by these studies the localization of HSC and rMF was analyzed in diseased livers. Normal and acutely as well as chronically
carbon tetrachloride-injured livers were analyzed by immunohistochemistry and by in situ hybridization. In normal livers HSC
[desmin/glial fibrillary acid protein (GFAP)-positive cells] were distributed in the hepatic parenchyma, while rMF (desmin/smooth
muscle alpha actin-positive, GFAP-negative cells colocalized with fibulin-2) were located in the portal field, the walls of
central veins, and only occasionally in the parenchyma. Acute liver injury was characterized almost exclusively by an increase
in the number of HSC, while the amount of rMF was nearly unchanged. In early stages of fibrosis, HSC and rMF were detected
within the developing scars. In advanced stages of fibrosis, HSC were mainly present at the scar–parenchymal interface, while
rMF accounted for the majority of the cells located within the scar. At every stage of fibrogenesis, rMF, in contrast to HSC,
were only occasionally detected in the hepatic parenchyma. HSC and rMF are present in normal and diseased livers in distinct
compartments and respond differentially to tissue injury. Acute liver injury is followed by an almost exclusive increase in
the number of HSC, while in chronically injured livers not only HSC but also rMF are involved in scar formation.
Accepted: 16 September 1999 相似文献
86.
Mazhari-Tabrizi R Blank M Mumberg D Funk M Schwarz RT Eckert V 《Glycoconjugate journal》1999,16(11):673-679
Heterologous complementation in yeast has been a successful tool for cloning and characterisation of genes from various organisms. Therefore we constructed conditionally lethal Saccharomyces cerevisiae strains by replacing the endogenous promoter from the genes of interest (glycosyltransferases) by the stringently regulated GAL1-promoter, by a technique called chromosomal promoter replacement. Such yeast strains were constructed for the genes Alg 1, Alg7, Sec59, Wbp1 involved in N-Glycosylation, the genes Gpi2, Gpi3/Spt14, Gaal, Pis1, involved in GPI-anchor biosynthesis and Dpm involved in both pathways. All strains show the expected conditionally lethal phenotype on glucose-containing medium when expression of the respective gene is turned off. 相似文献
87.
Dominik?Seelow Raffaello?Galli Siegrun?Mebus Hans-Peter?Sperling Hans?Lehrach Silke?SperlingEmail author 《BMC bioinformatics》2004,5(1):168
Background
Motivated by a biomedical database set up by our group, we aimed to develop a generic database front-end with embedded knowledge discovery and analysis features. A major focus was the human-oriented representation of the data and the enabling of a closed circle of data query, exploration, visualization and analysis. 相似文献88.
Schaer DJ Boretti FS Hongegger A Poehler D Linnscheid P Staege H Müller C Schoedon G Schaffner A 《Immunogenetics》2001,53(2):170-177
89.
The primary influenza A virus-specific CD8(+)-T-cell responses measured by tetramer staining of spleen, lymph node, and bronchoalveolar lavage (BAL) lymphocyte populations were similar in magnitude for conventional I-A(b+/+) and CD4(+)-T-cell-deficient I-A(b-/-) mice. Comparable levels of virus-specific cytotoxic-T-lymphocyte activity were detected in the inflammatory exudate recovered by BAL following challenge. However, both the size of the memory T-cell pool and the magnitude of the recall response in the lymphoid tissues (but not the BAL specimens) were significantly diminished in mice lacking the CD4(+) subset. Also, the rate of virus elimination from the infected respiratory tract slowed at low virus loads following challenge of na?ve and previously immunized I-A(b-/-) mice. Thus, though the capacity to mediate the CD8(+)-T-cell effector function is broadly preserved in the absence of concurrent CD4(+)-T-cell help, both the maintenance and recall of memory are compromised and the clearance of residual virus is delayed. These findings are consistent with mathematical models that predict virus-host dynamics in this, and other, models of infection. 相似文献
90.
The consensus concept for thermostability engineering of proteins: further proof of concept 总被引:13,自引:0,他引:13
Lehmann M Loch C Middendorf A Studer D Lassen SF Pasamontes L van Loon AP Wyss M 《Protein engineering》2002,15(5):403-411
Previously, we calculated a consensus amino acid sequence from 13 homologous fungal phytases. A synthetic gene was constructed and recombinantly expressed. Surprisingly, consensus phytase-1 was 15-26 degrees C more thermostable than all parent phytases used in its design [Lehmann et al. (2000)Protein Eng., 13, 49-57]. In the present study, inclusion of six further phytase sequences in the amino acid sequence alignment resulted in the replacement of 38 amino acid residues in either one or both of the new consensus phytases-10 and -11. Since consensus phytase-10, again, was 7.4 degrees C more thermostable than consensus phytase-1, the thermostability effects of most of the 38 amino acid substitutions were tested by site-directed mutagenesis. Both stabilizing and destabilizing mutations were identified, but all affected the stability of the enzyme by <3 degrees C. The combination of all stabilizing amino acid exchanges in a multiple mutant of consensus phytase-1 increased the unfolding temperature from 78.0 to 88.5 degrees C. Likewise, back-mutation of four destabilizing amino acids and introduction of an additional stabilizing amino acid in consensus phytase-10 further increased the unfolding temperature from 85.4 to 90.4 degrees C. The thermostabilization achieved is the result of a combination of slight improvements from multiple amino acid exchanges rather than being the effect of a single or of just a few dominating mutations that have been introduced by chance. The present findings support the general validity of the consensus concept for thermostability engineering of proteins. 相似文献