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101.
Alena Janda Ertan Eryilmaz Antonio Nakouzi David Cowburn Arturo Casadevall 《The Journal of biological chemistry》2012,287(42):35409-35417
The finding that the antibody (Ab) constant (C) region can influence fine specificity suggests that isotype switching contributes to the generation of Ab diversity and idiotype restriction. Despite the centrality of this observation for diverse immunological effects such as vaccine responses, isotype-restricted antibody responses, and the origin of primary and secondary responses, the molecular mechanism(s) responsible for this phenomenon are not understood. In this study, we have taken a novel approach to the problem by probing the paratope with 15N label peptide mimetics followed by NMR spectroscopy and fluorescence emission spectroscopy. Specifically, we have explored the hypothesis that the C region imposes conformational constraints on the variable (V) region to affect paratope structure in a V region identical IgG1, IgG2a, IgG2b, and IgG3 mAbs. The results reveal isotype-related differences in fluorescence emission spectroscopy and temperature-related differences in binding and cleavage of a peptide mimetic. We conclude that the C region can modify the V region structure to alter the Ab paratope, thus providing an explanation for how isotype can affect Ab specificity. 相似文献
102.
The thermostabilization of penicillin G acylase (PGA) obtained from a mutant of Escherichia coli ATCC 11105 by cross-linking with dextran dialdehyde molecules, at a molecular mass of 11 500, 37 700 and 71 000 Da, was studied.
The thermal inactivation mechanisms of the native and modified PGA were both considered to obey first-order inactivation kinetics
during prolonged heat treatment, forming fully active but temperature-sensitive transient states. The highest enhancement
to the thermostability of PGA was obtained using dextran-71000-dialdehyde modification, as a␣nearly ninefold increase at temperatures
above 50 °C. The modification of PGA by dextran-11500-dialdehyde resulted in a considerable reduction of the V
m and K
m parameters of the enzyme. However, other dextran dialdehyde derivatives used for modification did not cause a meaningful
change in either V
m and K
m. Modification by dextran dialdehyde derivatives did not result in significant change to either the optimal temperature or
the activation energy of PGA. All modified PGA preparations showed lower inactivation rate constants but higher half-lives
for inactivation than those of the native PGA at all temperatures studied. As indicated by the half-life times and k
i values, dextran 71000-dialdehyde was found to be more effective at cross-linking in the thermo-stabilization of PGA than
any other agent studied in this work.
Received: 3 December 1996 / Received revision: 17 March 1997 / Accepted: 22 March 1997 相似文献
103.
Effect of pituitary adenylate cyclase activating polypeptide on rat pancreatic exocrine secretion. 总被引:2,自引:0,他引:2
A novel neuropeptide, pituitary adenylate cyclase activating polypeptide (PACAP), which has been isolated from ovine hypothalami, shows 68% homology with vasoactive intestinal peptide (VIP). Since VIP stimulates amylase secretion from the pancreas, we investigated the effect of PACAP and VIP on rat pancreatic exocrine secretion after intravenous injections of PACAP-27, PACAP-38, or VIP at doses of 2.5, 5 or 10 nmol/kg. Results showed: 1) Bolus injection of PACAP stimulated pancreatic amylase and protein secretions in a dose-dependent manner; and 2) Stimulation of amylase secretion with 10 nmol/kg of PACAP-27 was greater than that induced with the same dose of VIP or PACAP-38 (p less than 0.05). 相似文献
104.
Martina Dávidová Radim Blažek Teodora Trichkova Emmanuil Koutrakis Özcan Gaygusuz Ertan Ercan Markéta Ondračková 《Aquatic Ecology》2011,45(3):377-387
In aquatic ecosystems, fish play a key role in parasite accumulation and transmission to predacious animals. In the present
study, realized on seven populations of a small cyprinid fish species, the European bitterling Rhodeus amarus, we investigated (1) the role of the European bitterling as a potential intermediate or paratenic host, (2) the ability of
the fish to accumulate parasites with similar final host group, and (3) its significance as a potential source of parasite
infection in the ecosystem in respect to habitat characteristics. A total of 36 parasite species were recorded; 31 species
(90% of all parasite specimens) were classified as endoparasites. Most of the endoparasites were found in the larval life
stage, using bitterling as an intermediate or paratenic host. In particular, parasite community structure showed significantly
higher proportions of allogenic parasites in comparison with autogenic. The supposed co-occurrence of parasite species with
identical final host groups showed only a weak association. The adjacent reservoir areas were a significant determinant of
both the total and infracommunity parasite species richness and for the mean parasite abundance. No relationship between the
distance of sampling site from the adjacent reservoir and parasite community characteristics was found. As a small-sized fish
with a wide distribution range and high local abundances, the European bitterling can represent a natural prey for a wide
range of piscivorous predators. Due to its susceptibility to the number of larval endoparasites, this fish species may therefore
fulfill the role as important transmitter of parasites to their final hosts. 相似文献
105.
Katja Kleinsteuber Kerrin Heesch Stefanie Schattling Malte Kohns Claudia Sander-Jülch Gerhard Walzl Anneke Hesseling Ertan Mayatepek Bernhard Fleischer Florian M. Marx Marc Jacobsen 《PloS one》2013,8(4)
The vast majority of Mycobacterium tuberculosis (M. tuberculosis) infected individuals are protected from developing tuberculosis and T cells are centrally involved in this process. MicroRNAs (miRNA) regulate T-cell functions and are biomarker candidates of disease susceptibility and treatment efficacy in M. tuberculosis infection. We determined the expression profile of 29 selected miRNAs in CD4+ T cells from tuberculosis patients and contacts with latent M. tuberculosis infection (LTBI). These analyses showed lower expression of miR-21, miR-26a, miR-29a, and miR-142-3p in CD4+ T cells from tuberculosis patients. Whole blood miRNA candidate analyses verified decreased expression of miR-26a, miR-29a, and miR-142-3p in children with tuberculosis as compared to healthy children with LTBI. Despite marked variances between individual donor samples, trends of increased miRNA candidate expression during treatment and recovery were observed. Functional in vitro analysis identified increased miR-21 and decreased miR-26a expression after re-stimulation of T cells. In vitro polarized Interleukin-17 positive T-cell clones showed activation-dependent miR-29a up-regulation. In order to characterize the role of miR-29a (a described suppressor of Interferon-γ in tuberculosis), we analyzed M. tuberculosis specific Interferon-γ expressing T cells in children with tuberculosis and healthy contacts but detected no correlation between miR-29a and Interferon-γ expression. Suppression of miR-29a in primary human T cells by antagomirs indicated no effect on Interferon-γ expression after in vitro activation. Finally, classification of miRNA targets revealed only a moderate overlap between the candidates. This may reflect differential roles of miR-21, miR-26a, miR-29a, and miR-142-3p in T-cell immunity against M. tuberculosis infection and disease. 相似文献
106.
107.
Nicole Abreu Soumaya Mannoubi Ertan Ozyamak David Pignol Nicolas Ginet Arash Komeili 《Journal of bacteriology》2014,196(17):3111-3121
Many bacterial species contain multiple actin-like proteins tasked with the execution of crucial cell biological functions. MamK, an actin-like protein found in magnetotactic bacteria, is important in organizing magnetosome organelles into chains that are used for navigation along geomagnetic fields. MamK and numerous other magnetosome formation factors are encoded by a genetic island termed the magnetosome island. Unlike most magnetotactic bacteria, Magnetospirillum magneticum AMB-1 (AMB-1) contains a second island of magnetosome-related genes that was named the magnetosome islet. A homologous copy of mamK, mamK-like, resides within this islet and encodes a protein capable of filament formation in vitro. Previous work had shown that mamK-like is expressed in vivo, but its function, if any, had remained unknown. Though MamK-like is highly similar to MamK, it contains a mutation that in MamK and other actins blocks ATPase activity in vitro and filament dynamics in vivo. Here, using genetic analysis, we demonstrate that mamK-like has an in vivo role in assisting organelle alignment. In addition, MamK-like forms filaments in vivo in a manner that is dependent on the presence of MamK and the two proteins interact in a yeast two-hybrid assay. Surprisingly, despite the ATPase active-site mutation, MamK-like is capable of ATP hydrolysis in vitro and promotes MamK filament turnover in vivo. Taken together, these experiments suggest that direct interactions between MamK and MamK-like contribute to magnetosome alignment in AMB-1. 相似文献
108.
Ertan Eryilmaz Neel H. Shah Tom W. Muir David Cowburn 《The Journal of biological chemistry》2014,289(21):14506-14511
Protein splicing is a posttranslational modification where intervening proteins (inteins) cleave themselves from larger precursor proteins and ligate their flanking polypeptides (exteins) through a multistep chemical reaction. First thought to be an anomaly found in only a few organisms, protein splicing by inteins has since been observed in microorganisms from all domains of life. Despite this broad phylogenetic distribution, all inteins share common structural features such as a horseshoe-like pseudo two-fold symmetric fold, several canonical sequence motifs, and similar splicing mechanisms. Intriguingly, the splicing efficiencies and substrate specificity of different inteins vary considerably, reflecting subtle changes in the chemical mechanism of splicing, linked to their local structure and dynamics. As intein chemistry has widespread use in protein chemistry, understanding the structural and dynamical aspects of inteins is crucial for intein engineering and the improvement of intein-based technologies. 相似文献
109.
110.
Bildik Gamze Esmaeilian Yashar Vatansever Dogan Bilir Esra Taskiran Cagatay Oktem Ozgur 《Molecular biology reports》2020,47(5):3789-3796
Molecular Biology Reports - We aimed to provide a comparative characterization of DNA damage response elements, survival/apoptosis and cell cycle progression of the malignant granulosa cells... 相似文献