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Site directed mutations

Clark Rosensweig, Kimberly A Reynolds, Peng Gao, Isara Laothamatas, Yongli Shan, Rama Ranganathan, Joseph S Takahashi, Carla B Green
Mammalian circadian clocks are driven by a transcription/translation feedback loop composed of positive regulators (CLOCK/BMAL1) and repressors (CRYPTOCHROME 1/2 (CRY1/2) and PER1/2). To understand the structural principles of regulation, we used evolutionary sequence analysis to identify co-evolving residues within the CRY/PHL protein family. Here we report the identification of an ancestral secondary cofactor-binding pocket as an interface in repressive CRYs, mediating regulation through direct interaction with CLOCK and BMAL1...
March 19, 2018: Nature Communications
Olga Y Rybina, Yakov M Rozovsky, Ekaterina R Veselkina, Elena G Pasyukova
Molecular mechanisms governing gene expression and defining complex phenotypes are central to understanding the basics of development and aging. Here, we demonstrate that naturally occurring polymorphisms of the Lim3 regulatory region that are associated with variation in gene expression and Drosophila lifespan control are located exclusively in the Polycomb response element (PRE). We find that the Polycomb group (PcG) protein Polycomb (PC) is bound to the PRE only in embryos where Lim3 is present in both repressed and active states...
March 16, 2018: Biochimica et Biophysica Acta
Haofeng Gao, Chanjuan Li, Ramesh Bandikari, Ziduo Liu, Nan Hu, Qiang Yong
BACKGROUND: In industries lipolytic reactions occur in insensitive conditions such as high temperature thus novel stout esterases with unique properties are attracts to the industrial application. Protein engineering is the tool to obtain desirable characters of enzymes. A novel esterase gene was isolated from South China Sea and subjected to a random mutagenesis and site directed mutagenesis for higher activity and thermo-stability compared to wild type. RESULTS: A novel esterase showed the highest hydrolytic activity against p-nitrophenyl acetate (pNPA, C2) and the optimal activity at 40 °C and pH 8...
March 19, 2018: Microbial Cell Factories
Xi Chen, Steven D Schwartz
In this article we study how directed evolution in the Kemp Eliminase family of artificial enzymes makes differential use of rapid rate promoting vibrations as a component of their chemical mechanism. Even though this family was initially created by placing the expected active site in a fixed protein matrix, we find a shift from largely static to more dynamic active sites that make use of donor acceptor compression as the evolutionary process proceeds. We see this introduction of dynamics significantly shifts the order of processes in the reaction...
March 19, 2018: Biochemistry
Mei-Yi Lu, Syuan-Shao Lu, Shiann-Luen Chang, Fang Liao
CCR6 is a G protein-coupled receptor (GPCR) that recognizes a single chemokine ligand, CCL20 and is primarily expressed by leukocytes. Upon ligand binding, CCR6 activates Gαi heterotrimeric G proteins to induce various potential cellular outcomes through context-specific cell signaling. It is well known that differential phosphorylation of Ser and Thr residues in the C-terminal domains or intracellular loops of GPCRs can generate barcodes that regulate GPCR function by regulating the recruitment of β-arrestins...
2018: Frontiers in Immunology
Marco A Alfonzo-Méndez, Gabriel Carmona-Rosas, David A Hernández-Espinosa, M Teresa Romero-Ávila, J Adolfo García-Sáinz
Human α1D -adrenoceptors (α1D -ARs) are a group of the seven transmembrane-spanning proteins that mediate many of the physiological and pathophysiological actions of adrenaline and noradrenaline. Although it is known that α1D -ARs are phosphoproteins, their specific phosphorylation sites and the kinases involved in their phosphorylation remain largely unknown. Using a combination of in silico analysis, mass spectrometry and site directed mutagenesis, we identified distinct α1D -AR phosphorylation patterns during noradrenaline- or phorbol ester-mediated desensitizations...
March 15, 2018: Biochimica et Biophysica Acta
Breann L Brown, Julia R Kardon, Robert T Sauer, Tania A Baker
5-Aminolevulinic acid synthase (ALAS) catalyzes the first step in heme biosynthesis. We present the crystal structure of a eukaryotic ALAS from Saccharomyces cerevisiae. In this homodimeric structure, one ALAS subunit contains covalently bound cofactor, pyridoxal 5'-phosphate (PLP), whereas the second is PLP free. Comparison between the subunits reveals PLP-coupled reordering of the active site and of additional regions to achieve the active conformation of the enzyme. The eukaryotic C-terminal extension, a region altered in multiple human disease alleles, wraps around the dimer and contacts active-site-proximal residues...
March 5, 2018: Structure
Xinjian Yin, Jianping Wu, Lirong Yang
The objective of this study was to identify and exploit a robust biocatalyst that can be applied in reductive amination for enantioselective synthesis of the competitive herbicide L-phosphinothricin. Applying a genome mining-based library construction strategy, eight NADPH-specific glutamate dehydrogenases (GluDHs) were identified for reductively aminating 2-oxo-4-[(hydroxy)(methyl)phosphinoyl]butyric acid (PPO) to L-phosphinothricin. Among them, the glutamate dehydrogenase cloned from Pseudomonas putida (PpGluDH) exhibited relatively high catalytic activity and favorable soluble expression...
March 16, 2018: Applied Microbiology and Biotechnology
Yoshinori Hirano, Yu Amano, Shigenobu Yonemura, Toshio Hakoshima
Mechanotransduction by α-catenin facilitates the force-dependent development of adherens junctions (AJs) by recruiting vinculin to reinforce actin anchoring of AJs. The α-catenin mechanotransducing action is facilitated by its force-sensing device region that autoinhibits the vinculin-binding site 1 (VBS1). Here, we report the high-resolution structure of the force-sensing device region of α-catenin, which shows the autoinhibited form comprised of helix bundles E, F and G. The cryptic VBS1 is embedded into helix bundle E stabilized by direct interactions with the autoinhibitory region forming helix bundles F and G...
March 15, 2018: Genes to Cells: Devoted to Molecular & Cellular Mechanisms
Eva K Brinkman, Arne N Kousholt, Tim Harmsen, Christ Leemans, Tao Chen, Jos Jonkers, Bas van Steensel
Template-directed CRISPR/Cas9 editing is a powerful tool for introducing subtle mutations in genomes. However, the success rate of incorporation of the desired mutations at the target site is difficult to predict and therefore must be empirically determined. Here, we adapted the widely used TIDE method for quantification of templated editing events, including point mutations. The resulting TIDER method is a rapid, cheap and accessible tool for testing and optimization of template-directed genome editing strategies...
March 10, 2018: Nucleic Acids Research
Ping Hu, Fengchang Qiao, Yan Wang, Lulu Meng, Xiuqing Ji, Chunyu Luo, Tianhui Xu, Ran Zhou, Jingjing Zhang, Bin Yu, Leilei Wang, Ting Wang, Qiong Pan, Dingyuan Ma, Dong Liang, Zhengfeng Xu
OBJECTIVES: This study aimed to determine the diagnostic yield of targeted next-generation sequencing (NGS) in prenatal diagnosis of congenital heart defects (CHDs) and for investigating the possible genetic etiology of prenatal CHD cases. METHODS: Forty-four fetuses with CHDs and normal molecular karyotypes underwent targeted NGS in this study. Fetal genomic DNA was directly extracted from amniotic fluid cells in each prenatal case. A customized targeted NGS panel containing 77 CHD-associated genes was designed to detect variants in the coding regions and the splicing sites of these genes...
March 13, 2018: Ultrasound in Obstetrics & Gynecology
Mengzhu Li, Hong Deng, Rui Ma, Huiying Luo, Bin Yao, Xiaoyun Su
Pyranose oxidase (POx) is a homotetrameric flavoprotein that catalyzes the oxidation of pyranose-configured sugars at position C-2 to corresponding 2-ketoaldoses. The wide substrate specificity makes POx potential for application in various biotechnological industries. In the present study we reported the gene cloning and heterologous expression of a POx from the basidiomycete Trametes sp. and functionally expressed the gene in Escherichia coli BL21(DE3). Based on sequence alignment, three residues were chosen for site-directed mutagenesis to obtain two single mutants (K312E and E539K) and two double mutants (T166A/E539K and K312E/E539K)...
March 13, 2018: AMB Express
Carla Danussi, Promita Bose, Prasanna T Parthasarathy, Pedro C Silberman, John S Van Arnam, Mark Vitucci, Oliver Y Tang, Adriana Heguy, Yuxiang Wang, Timothy A Chan, Gregory J Riggins, Erik P Sulman, Frederick Lang, Chad J Creighton, Benjamin Deneen, C Ryan Miller, David J Picketts, Kasthuri Kannan, Jason T Huse
Mutational inactivation of the SWI/SNF chromatin regulator ATRX occurs frequently in gliomas, the most common primary brain tumors. Whether and how ATRX deficiency promotes oncogenesis by epigenomic dysregulation remains unclear, despite its recent implication in both genomic instability and telomere dysfunction. Here we report that Atrx loss recapitulates characteristic disease phenotypes and molecular features in putative glioma cells of origin, inducing cellular motility although also shifting differentiation state and potential toward an astrocytic rather than neuronal histiogenic profile...
March 13, 2018: Nature Communications
Ying Pang, Garima Gupta, Chunzhang Yang, Herui Wang, Thanh-Truc Huynh, Ziedulla Abdullaev, Svetlana D Pack, Melanie J Percy, Terence R J Lappin, Zhengping Zhuang, Karel Pacak
BACKGROUND: The role of the hypoxia signaling pathway in the pathogenesis of pheochromocytoma/paraganglioma (PPGL)-polycythemia syndrome has been elucidated. Novel somatic mutations in hypoxia-inducible factor type 2A (HIF2A) and germline mutations in prolyl hydroxylase type 1 and type 2 (PHD1 and PHD2) have been identified to cause upregulation of the hypoxia signaling pathway and its target genes including erythropoietin (EPO) and its receptor (EPOR). However, in a minority of patients presenting with this syndrome, the genetics and molecular pathogenesis remain unexplained...
March 13, 2018: BMC Cancer
Ke Xiong, Suyue Xiong, Siyu Gao, Qin Li, Baoguo Sun, Xiuting Li
The preparation of oligosaccharides via xylan hydrolysis is an effective way to add value to hemicellulosic material of agricultural waste. The bacterial strain Streptomyces L10608, isolated from soil, contains genes encoding xylanases of glucoside hydrolase family 10/11 (GH10/11), and these have been cloned to catalyze the production of xylooligosaccharide (XOS). To improve the XOS proportion of hydrolysates produced by xylanase, four amino acid residues were substituted by site-directed mutagenesis, and the mutant genes were overexpressed in Escherichia coli ...
March 13, 2018: International Journal of Molecular Sciences
Maria Agthe, Yvonne Garbers, Joachim Grötzinger, Christoph Garbers
BACKGROUND/AIMS: The cytokine interleukin-11 (IL-11) has important pro- and anti-inflammatory functions. It activates its target cells through binding to the IL-11 receptor (IL-11R), and the IL-11/IL-11R complex recruits a homodimer of glycoprotein 130 (gp130). N-linked glycosylation, a post-translational modification where complex oligosaccharides are attached to the side chain of asparagine residues, is often important for stability, folding and biological function of cytokine receptors...
March 7, 2018: Cellular Physiology and Biochemistry
Tom H Wright, Benjamin G Davis
Methods for installing natural and unnatural amino acids and their modifications into proteins in a benign and precise manner are highly sought-after in protein science. Here we describe a protocol for 'post-translational mutagenesis' that enables the programmed installation of protein side chains through the use of rapid, mild and operationally simple free-radical chemistry performed on recombinantly expressed and purified proteins. By introduction of protein dehydroalanine (Dha) residues (in this instance, from a unique cysteine residue introduced by site-directed mutagenesis) as free-radical trapping 'tags' for downstream modification, exquisite control over the site of subsequent modification is achieved...
October 2017: Nature Protocols
Timothy Palzkill
The most common mechanism of resistance to β-lactam antibiotics in Gram-negative bacteria is the production of β-lactamases that hydrolyze the drugs. Class A β-lactamases are serine active-site hydrolases that include the common TEM, CTX-M, and KPC enzymes. The TEM enzymes readily hydrolyze penicillins and older cephalosporins. Oxyimino-cephalosporins, such as cefotaxime and ceftazidime, however, are poor substrates for TEM-1 and were introduced, in part, to circumvent β-lactamase-mediated resistance. Nevertheless, the use of these antibiotics has lead to evolution of numerous variants of TEM with mutations that significantly increase the hydrolysis of the newer cephalosporins...
2018: Frontiers in Molecular Biosciences
Pavel Bashtrykov, Albert Jeltsch
The discovery and adaptation of the CRISPR/Cas system for epigenome editing has allowed for a straightforward design of targeting modules which can direct epigenetic editors to virtually any genomic site. This advancement in DNA-targeting technology brings allele-specific epigenome editing into reach, a "super-specific" variation of epigenome editing whose goal is an alteration of chromatin marks at only one selected allele of the target genomic locus. This technology would be useful for the treatment of diseases caused by a mutant allele with a dominant effect, because allele-specific epigenome editing allows the specific silencing of the mutated allele leaving the healthy counterpart expressed...
2018: Methods in Molecular Biology
Mohamed E Salem, Alberto Puccini, Axel Grothey, Derek Raghavan, Richard M Goldberg, Joanne Xiu, W Michael Korn, Benjamin A Weinberg, Jimmy J Hwang, Anthony F Shields, John L Marshall, Philip A Philip, Heinz-Josef Lenz
The efficacy of immunotherapy varies widely among different gastrointestinal cancers. Response to immune checkpoint inhibitors is shown to correlate with tumor mutation load (TML), mismatch repair deficiency (dMMR) status, and programmed cell death-ligand 1 (PD-L1) expression. Herein, we quantify TML, dMMR, and PD-L1 expression and determine their interrelationship in gastrointestinal cancers. Here, a total of 4125 tumors from 14 different gastrointestinal cancer sites were studied using validated assays. Next-generation sequencing (NGS) was performed on genomic DNA isolated from formalin-fixed paraffin-embedded (FFPE) tumor specimens using the NextSeq platform...
March 9, 2018: Molecular Cancer Research: MCR
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