排序方式: 共有97条查询结果,搜索用时 15 毫秒
91.
Aachmann FL Svanem BI Güntert P Petersen SB Valla S Wimmer R 《The Journal of biological chemistry》2006,281(11):7350-7356
In the bacterium Azotobacter vinelandii, a family of seven secreted and calcium-dependent mannuronan C-5 epimerases (AlgE1-7) has been identified. These epimerases are responsible for the epimerization of beta-d-mannuronic acid to alpha-l-guluronic acid in alginate polymers. The epimerases consist of two types of structural modules, designated A (one or two copies) and R (one to seven copies). The structure of the catalytically active A-module from the smallest epimerase AlgE4 (consisting of AR) has been solved recently. This paper describes the NMR structure of the R-module from AlgE4 and its titration with a substrate analogue and paramagnetic thulium ions. The R-module folds into a right-handed parallel beta-roll. The overall shape of the R-module is an elongated molecule with a positively charged patch that interacts with the substrate. Titration of the R-module with thulium indicated possible calcium binding sites in the loops formed by the nonarepeat sequences in the N-terminal part of the molecule and the importance of calcium binding for the stability of the R-module. Structure calculations showed that calcium ions can be incorporated in these loops without structural violations and changes. Based on the structure and the electrostatic surface potential of both the A- and R-module from AlgE4, a model for the appearance of the whole protein is proposed. 相似文献
92.
Valla J Schneider L Niedzielko T Coon KD Caselli R Sabbagh MN Ahern GL Baxter L Alexander G Walker DG Reiman EM 《Mitochondrion》2006,6(6):323-330
Mitochondrial abnormalities are found in Alzheimer's disease (AD), but previous reports have not examined at-risk groups. In subjects with AD, mild cognitive impairment (MCI), and non-demented aged controls, platelet and lymphocyte mitochondria were isolated and analyzed for Complexes I, III, and IV of the electron transport chain. Western blots were used to control for differential enrichment of samples. Results demonstrated significant declines in Complexes III and IV in AD, and a significant decline in Complex IV in MCI. This report confirms mitochondrial deficiencies in AD, extends them to MCI, and suggests they are present at the earliest symptomatic stages of disease. 相似文献
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94.
D Arsène J C Verwaerde A Rideau J C Sassier A Valla M Thomas 《Revue fran?aise de transfusion et immuno-hématologie》1983,26(1):45-65
175 Chronic HBs Ag carriers have been discovered in the blood donors of the Calvados blood transfusion center from 1971 to 1979. 72 of them (41%) gave their consent for a clinical and biological study at the end of 1979, after receiving a convocation letter. This work had two aims: - to study the epidemiological factors in this population. - to evaluate the clinical and biological consequences of persistent antigenemia. 1. Epidemiological Study. Most results agree with the literature (higher prevalence in male, age, stay in endemic countries) but some results disagree for several reasons: our donors are all volunteers, HBs Ag prevalence is low in our region, most of the patients are caucasian and with life conditions and habits which may explain some particularities in contagion. Furthermore, the relative number of blood donors found every year as chronic HBs Ag carriers, does not increase in our country. 2. The Clinical and Biological follow-up of 62 HBs Ag carriers (alcoholics excluded) was carried out for 4,3 years on average. No patients developed clinical and biological features of chronic liver disease. After a mean term follow-up, we conclude that the asymptomatic HBs Ag carriers state seems not to be of bad prognostic. Since long term complications cannot be excluded, the follow-up of these patients must be maintained. 相似文献
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96.
The Presence of N-Terminal Secretion Signal Sequences Leads to Strong Stimulation of the Total Expression Levels of Three Tested Medically Important Proteins during High-Cell-Density Cultivations of Escherichia coli
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97.
Susan Maleki Eivind Almaas Sergey Zotchev Svein Valla Helga Ertesv?g 《Applied and environmental microbiology》2016,82(4):1227-1236
Pseudomonas fluorescens is able to produce the medically and industrially important exopolysaccharide alginate. The proteins involved in alginate biosynthesis and secretion form a multiprotein complex spanning the inner and outer membranes. In the present study, we developed a method by which the porin AlgE was detected by immunogold labeling and transmission electron microscopy. Localization of the AlgE protein was found to depend on the presence of other proteins in the multiprotein complex. No correlation was found between the number of alginate factories and the alginate production level, nor were the numbers of these factories affected in an algC mutant that is unable to produce the precursor needed for alginate biosynthesis. Precursor availability and growth phase thus seem to be the main determinants for the alginate production rate in our strain. Clustering analysis demonstrated that the alginate multiprotein complexes were not distributed randomly over the entire outer cell membrane surface. 相似文献