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991.
Jianli Gong Yongneng Yao Pingbo Zhang Barath Udayasuryan Elena V. Komissarova Ju Chen Sivaraj Sivaramakrishnan Jennifer E. Van Eyk Susan F. Steinberg 《Molecular and cellular biology》2015,35(10):1727-1740
The diverse roles of protein kinase C-δ (PKCδ) in cellular growth, survival, and injury have been attributed to stimulus-specific differences in PKCδ signaling responses. PKCδ exerts membrane-delimited actions in cells activated by agonists that stimulate phosphoinositide hydrolysis. PKCδ is released from membranes as a Tyr313-phosphorylated enzyme that displays a high level of lipid-independent activity and altered substrate specificity during oxidative stress. This study identifies an interaction between PKCδ''s Tyr313-phosphorylated hinge region and its phosphotyrosine-binding C2 domain that controls PKCδ''s enzymology indirectly by decreasing phosphorylation in the kinase domain ATP-positioning loop at Ser359. We show that wild-type (WT) PKCδ displays a strong preference for substrates with serine as the phosphoacceptor residue at the active site when it harbors phosphomimetic or bulky substitutions at Ser359. In contrast, PKCδ-S359A displays lipid-independent activity toward substrates with either a serine or threonine as the phosphoacceptor residue. Additional studies in cardiomyocytes show that oxidative stress decreases Ser359 phosphorylation on native PKCδ and that PKCδ-S359A overexpression increases basal levels of phosphorylation on substrates with both phosphoacceptor site serine and threonine residues. Collectively, these studies identify a C2 domain-pTyr313 docking interaction that controls ATP-positioning loop phosphorylation as a novel, dynamically regulated, and physiologically relevant structural determinant of PKCδ catalytic activity. 相似文献
992.
Denis Susorov Tatiana Mikhailova Alexander Ivanov Elizaveta Sokolova Elena Alkalaeva 《Nucleic acids research》2015,43(6):3332-3343
Stabilization of the ribosomal complexes plays an important role in translational control. Mechanisms of ribosome stabilization have been studied in detail for initiation and elongation of eukaryotic translation, but almost nothing is known about stabilization of eukaryotic termination ribosomal complexes. Here, we present one of the mechanisms of fine-tuning of the translation termination process in eukaryotes. We show that certain deacylated tRNAs, remaining in the E site of the ribosome at the end of the elongation cycle, increase the stability of the termination and posttermination complexes. Moreover, only the part of eRF1 recognizing the stop codon is stabilized in the A site of the ribosome, and the stabilization is not dependent on the hydrolysis of peptidyl-tRNA. The determinants, defining this property of the tRNA, reside in the acceptor stem. It was demonstrated by site-directed mutagenesis of tRNAVal and construction of a mini-helix structure identical to the acceptor stem of tRNA. The mechanism of this stabilization is different from the fixation of the unrotated state of the ribosome by CCA end of tRNA or by cycloheximide in the E site. Our data allow to reveal the possible functions of the isodecoder tRNAs in eukaryotes. 相似文献
993.
Elena Sugrue Nicholas J. Fraser Davis H. Hopkins Paul D. Carr Jeevan L. Khurana John G. Oakeshott Colin Scott Colin J. Jackson 《Applied and environmental microbiology》2015,81(7):2612-2624
The amidohydrolase superfamily has remarkable functional diversity, with considerable structural and functional annotation of known sequences. In microbes, the recent evolution of several members of this family to catalyze the breakdown of environmental xenobiotics is not well understood. An evolutionary transition from binuclear to mononuclear metal ion coordination at the active sites of these enzymes could produce large functional changes such as those observed in nature, but there are few clear examples available to support this hypothesis. To investigate the role of binuclear-mononuclear active-site transitions in the evolution of new function in this superfamily, we have characterized two recently evolved enzymes that catalyze the hydrolysis of the synthetic herbicides molinate (MolA) and phenylurea (PuhB). In this work, the crystal structures, mutagenesis, metal ion analysis, and enzyme kinetics of both MolA and PuhB establish that these enzymes utilize a mononuclear active site. However, bioinformatics and structural comparisons reveal that the closest putative ancestor of these enzymes had a binuclear active site, indicating that a binuclear-mononuclear transition has occurred. These proteins may represent examples of evolution modifying the characteristics of existing catalysts to satisfy new requirements, specifically, metal ion rearrangement leading to large leaps in activity that would not otherwise be possible. 相似文献
994.
Elena?G.?RudikovskayaEmail author Lyubov?V.?Dudareva Aleksandr?A.?Shishparenok Aleksandr?V.?Rudikovskii 《Acta Physiologiae Plantarum》2015,37(11):238
For the first time, we have studied the polyphenolic profile of fruits of Siberian crabapple and its hybrids (F1, F2, and F3) with domestic apple cultivated in East Siberia. It is shown that the chemical composition of polyphenolics of Siberian crabapple fruits is overwhelmingly characteristic of the genus Malus; on the other hand, it has clearly identifiable features: low content of flavan-3-ols and derivatives of cinnamic acid; high content of procyanidin B1, phloridzin, anthocyanes, and quercetin glycosides. Procyanidin B2 was not found in both peel and flesh of Siberian crabapple. In the case of hybridization with domestic apple, the fruits of resulting cultivars show a substantial change in the flavan-3-ol content ratio because of the synthesizing of procyanidin B2 in tissues and an increase in (?)-epicatechin content. 相似文献
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Listeria monocytogenes exopolysaccharide: origin,structure, biosynthetic machinery and c‐di‐GMP‐dependent regulation 下载免费PDF全文
Volkan K. Köseoğlu Christian Heiss Parastoo Azadi Elena Topchiy Zehra T. Güvener Teresa E. Lehmann Kurt W. Miller Mark Gomelsky 《Molecular microbiology》2015,96(4):728-743
Elevated levels of the second messenger c‐di‐GMP activate biosynthesis of an unknown exopolysaccharide (EPS) in the food‐borne pathogen Listeria monocytogenes. This EPS strongly protects cells against disinfectants and desiccation, indicating its potential significance for listerial persistence in the environment and for food safety. We analyzed the potential phylogenetic origin of this EPS, determined its complete structure, characterized genes involved in its biosynthesis and hydrolysis and identified diguanylate cyclases activating its synthesis. Phylogenetic analysis of EPS biosynthesis proteins suggests that they have evolved within monoderms. Scanning electron microscopy revealed that L. monocytogenes EPS is cell surface‐bound. Secreted carbohydrates represent exclusively cell‐wall debris. Based on carbohydrate composition, linkage and NMR analysis, the structure of the purified EPS is identified as a β‐1,4‐linked N‐acetylmannosamine chain decorated with terminal α‐1,6‐linked galactose. All genes of the pssA‐E operon are required for EPS production and so is a separately located pssZ gene. We show that PssZ has an EPS‐specific glycosylhydrolase activity. Exogenously added PssZ prevents EPS‐mediated cell aggregation and disperses preformed aggregates, whereas an E72Q mutant in the presumed catalytic residue is much less active. The diguanylate cyclases DgcA and DgcB, whose genes are located next to pssZ, are primarily responsible for c‐di‐GMP‐dependent EPS production. 相似文献