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Unstructured Proteins

Masayuki Onishi, John R Pringle
The unicellular green alga Chlamydomonas reinhardtii is a model organism that provides an opportunity to understand the evolution and functional biology of the lineage that includes the land plants, as well as aspects of the fundamental core biology conserved throughout the eukaryotic phylogeny. Although many tools are available to facilitate genetic, molecular biological, biochemical, and cell biological studies in Chlamydomonas, expression of unselected transgenes of interest (GOIs) has been challenging. In most methods used previously, the GOI and a selectable marker are expressed from two separate mRNAs, so that their concomitant expression is not guaranteed...
October 21, 2016: G3: Genes—Genomes—Genetics
Jenna F DuMond, Xue Zhang, Yuichiro Izumi, Kevin Ramkissoon, Guanghui Wang, Marjan Gucek, Xujing Wang, Maurice B Burg, Joan D Ferraris
NFAT5 is a transcription factor originally identified because it is activated by hypertonicity and that activation increases expression of genes that protect against the adverse effects of the hypertonicity. However, its targets also include genes not obviously related to tonicity. The transactivating domain of NFAT5 is contained in its c-terminal region, which is predicted to be unstructured. Unstructured regions are common in transcription factors particularly in transactivating domains where they can bind co-regulatory proteins essential to their function...
October 7, 2016: Physiological Genomics
Christoph Göbl, Moritz Resch, Madeleine Strickland, Christoph Hartlmüller, Martin Viertler, Nico Tjandra, Tobias Madl
The study of intrinsically disordered proteins (IDPs) by NMR often suffers from highly overlapped resonances that prevent unambiguous chemical-shift assignments, and data analysis that relies on well-separated resonances. We present a covalent paramagnetic lanthanide-binding tag (LBT) for increasing the chemical-shift dispersion and facilitating the chemical-shift assignment of challenging, repeat-containing IDPs. Linkage of the DOTA-based LBT to a cysteine residue induces pseudo-contact shifts (PCS) for resonances more than 20 residues from the spin-labeling site...
October 20, 2016: Angewandte Chemie
Anna Juhasova, Martina Baliova, Frantisek Jursky
Coomassie Brilliant Blue interacts with proteins and even though the interactions exhibit variation due to the amino acid content, reported dye interactions with individual proteins appear to be relatively stable. Here we report an atypical dynamic interaction of glycine transporters 1 and 2 N-termini with Coomassie dye, resulting in intramolecular interference with their Bradford assay. These proteins exhibit classic protein-Coomassie G-250 complex with absorption maximum at 595 nm, which within minutes starts to decrease and parallel increase of absorbance shoulders above 300 and 700 nm is observed...
October 15, 2016: Protein Journal
Géraldine Klein, Christelle Mathé, Mathilde Biola-Clier, Stéphanie Devineau, Emilie Drouineau, Elie Hatem, Laurent Marichal, Béatrice Alonso, Jean-Charles Gaillard, Gilles Lagniel, Jean Armengaud, Marie Carrière, Stéphane Chédin, Yves Boulard, Serge Pin, Jean-Philippe Renault, Jean-Christophe Aude, Jean Labarre
Upon contact with biological fluids, nanoparticles (NPs) are readily coated by cellular compounds, particularly proteins, which are determining factors for the localization and toxicity of NPs in the organism. Here, we improved a methodological approach to identify proteins that adsorb on silica NPs with high affinity. Using large-scale proteomics and mixtures of soluble proteins prepared either from yeast cells or from alveolar human cells, we observed that proteins with large unstructured region(s) are more prone to bind on silica NPs...
October 5, 2016: Nanotoxicology
Manoj Prasad, Anna N Walker, Jasmeet Kaur, James L Thomas, Shirley A Powell, Amit V Pandey, Randy M Whittal, William E Burak, Guy Petruzzelli, Himangshu S Bose
The acute response to stress consists of a series of physiological programs to promote survival by generating glucocorticoids and activating stress-response genes that increase the synthesis of many chaperone proteins specific to individual organelles. In the endoplasmic reticulum (ER), short-term stress triggers activation of the unfolded protein response (UPR) module that either leads to neutralization of the initial stress or adaption to it; chronic stress favors cell death. UPR induces expression of the transcription factor, C/EBP homology protein (CHOP), and its deletion protects against the lethal consequences of prolonged UPR...
October 3, 2016: Molecular and Cellular Biology
Chetana Baliga, Raghavan Varadarajan, Nilesh Aghera
The existence of parallel pathways in the folding of proteins seems intuitive, yet remains controversial. We explore the folding kinetics of the homodimeric E. coli toxin CcdB using multiple optical probes and approaches. Kinetic studies performed as a function of protein and denaturant concentrations demonstrate that the folding of CcdB is a four-state process. The two intermediates populated during folding are present on parallel pathways. Both form by rapid association of the monomers in a diffusion limited manner and appear to be largely unstructured, as they are silent to the optical probes employed in the current study...
October 4, 2016: Biochemistry
Oleg Laptenko, David R Tong, James Manfredi, Carol Prives
The p53 tumor suppressor is a transcription factor (TF) that exerts antitumor functions through its ability to regulate the expression of multiple genes. Within the p53 protein resides a relatively short unstructured C-terminal domain (CTD) that remarkably participates in virtually every aspect of p53 performance as a TF. Because these aspects are often interdependent and it is not always possible to dissect them experimentally, there has been a great deal of controversy about the CTD. In this review we evaluate the significance and key features of this interesting region of p53 and its impact on the many aspects of p53 function in light of previous and more recent findings...
September 23, 2016: Trends in Biochemical Sciences
Linlin Ma, Fan Yang, Simon Vu, Jie Zheng
TRPV1 is a polymodal nociceptor for diverse physical and chemical stimuli that interact with different parts of the channel protein. Recent cryo-EM studies revealed detailed channel structures, opening the door for mapping structural elements mediating activation by each stimulus. Towards this goal, here we have combined unstructured peptide-insertion screening (UPS) with electrophysiological and fluorescence recordings to explore structural and functional roles of the intracellular regions of TRPV1 in mediating various activation stimuli...
September 26, 2016: Scientific Reports
Bruno Lopes de Sousa, Celso Shiniti Nagano, Rafael da Conceição Simões, José Caetano Silva-Filho, Rodrigo Maranguape da Silva Cunha, João Batista Cajazeiras, Kyria Santiago do Nascimento, Benildo Sousa Cavada
Legume lectins have been widely studied and applied for many purposes in the last few decades, but many of their physiological aspects remain elusive. The Diocleinae legume subtribe, which includes intensively explored lectins, such as ConA, presents an unusual and extensive post-translational process which results in minor alterations in protein structure, in turn making its function elusive. Despite previous reports about Diocleinae precursor activity, no structural or functional analyses have ever been carried out to understand the impacts of post-translational processing relative to lectin structure and binding specificity...
September 21, 2016: Biochimie
Manisha Sharma, Cara Jamieson, Christina Lui, Beric R Henderson
β-catenin is a key mediator of Wnt signaling and its deregulated nuclear accumulation can drive cancer progression. While the central armadillo (Arm) repeats of β-catenin stimulate nuclear entry, the N- and C-terminal "tail" sequences are thought to regulate turnover and transactivation. We show here that the N- and C-tails are also potent transport sequences. The unstructured tails of β-catenin, when individually fused to a GFP-reporter, could enter and exit the nucleus rapidly in live cells. Proximity ligation assays and pull-down assays identified a weak interaction between the tail sequences and the FG-repeats of nucleoporins, consistent with a possible direct translocation of β-catenin through the nuclear pore complex...
September 19, 2016: Experimental Cell Research
Robert L Evans, John A Latham, Judith P Klinman, Carrie M Wilmot, Youlin Xia
The ribosomally synthesized and post-translationally modified peptide (RiPP), pyrroloquinoline quinone (PQQ), is a dehydrogenase cofactor synthesized by, but not exclusively used by, certain prokaryotes. RiPPs represent a rapidly expanding and diverse class of natural products-many of which have therapeutic potential-and the biosynthetic pathways for these are gaining attention. Five gene products from the pqq operon (PqqA, PqqB, PqqC, PqqD, and PqqE) are essential for PQQ biosynthesis. The substrate is the peptide PqqA, which is presented to the radical SAM enzyme PqqE by the small protein PqqD...
October 2016: Biomolecular NMR Assignments
Patrick Ernst, Andreas Plückthun
The specific recognition of peptides, which we define to include unstructured regions or denatured forms of proteins, is an intrinsic part of a multitude of biochemical assays and procedures. Many cellular interactions are based on this principle as well. While it would be highly desirable to have a stockpile of sequence-specific binders for essentially any sequence, a de novo selection of individual binders against every possible target peptide sequence would be rather difficult to reduce to practice. Modular peptide binders could overcome this problem, as preselected and/or predesigned modules could be reused for the generation of new binders and thereby revolutionize the generation of binding proteins...
September 16, 2016: Biological Chemistry
Matthias Wittwer, Sonja A Dames
Mycobacterium tuberculosis protein kinase G (PknG) is a 82 kDa multidomain eukaryotic-like serine/threonine kinase mediating the survival of pathogenic mycobacteria within host macrophages. The N-terminal sequence preceding the catalytic kinase domain contains an approximately 75 residues long tail, which was predicted to show no regulatory secondary structure (1-75 = NORS) but harbors the major in vivo phosphorylation site (T63), and a rubredoxin-like metal binding motif (74-147 = RD). In the reduced rubredoxin motif, four conserved cysteine residues that are present as two C-X-X-C-G motifs coordinate a metal ion...
October 2016: Biomolecular NMR Assignments
Daniele Cartelli, Alessandro Aliverti, Alberto Barbiroli, Carlo Santambrogio, Enzio M Ragg, Francesca V M Casagrande, Francesca Cantele, Silvia Beltramone, Jacopo Marangon, Carmelita De Gregorio, Vittorio Pandini, Marco Emanuele, Evelina Chieregatti, Stefano Pieraccini, Staffan Holmqvist, Luigi Bubacco, Laurent Roybon, Gianni Pezzoli, Rita Grandori, Isabelle Arnal, Graziella Cappelletti
α-Synuclein is a presynaptic protein associated to Parkinson's disease, which is unstructured when free in the cytoplasm and adopts α helical conformation when bound to vesicles. After decades of intense studies, α-Synuclein physiology is still difficult to clear up due to its interaction with multiple partners and its involvement in a pletora of neuronal functions. Here, we looked at the remarkably neglected interplay between α-Synuclein and microtubules, which potentially impacts on synaptic functionality...
2016: Scientific Reports
Alexander S Jones, James I Austerberry, Rana Dajani, Jim Warwicker, Robin Curtis, Jeremy P Derrick, Colin Robinson
The Tat system transports folded proteins across the bacterial plasma membrane, and in Escherichia coli preferentially transports correctly-folded proteins. Little is known of the mechanism by which Tat proofreads a substrate's conformational state, and in this study we have addressed this question using a heterologous single-chain variable fragment (scFv) with a defined structure. We introduced mutations to surface residues while leaving the folded structure intact, and also tested the importance of conformational flexibility...
September 13, 2016: Biochimica et Biophysica Acta
Emmanuel W Smith, Eric M Lewandowski, Natasha A Moussouras, Kyle G Kroeck, Brian F Volkman, Christopher T Veldkamp, Yu Chen
CCL21 chemokine binds the G protein-coupled receptor CCR7, aiding not only in immune response but also in cancer metastasis. Compared with other chemokines, CCL21 has a unique extended unstructured C-terminus that is truncated in some naturally occurring variants. We have determined the X-ray crystallographic structure of a truncated CCL21 (residues 1-79) lacking the extended C-terminus and identified, via two-dimensional nuclear magnetic resonance (NMR), a putative sulfotyrosine-binding site that may recognize such post-translationally modified tyrosine residues on the receptor...
October 11, 2016: Biochemistry
Neelam Dabas Sen, Fujun Zhou, Michael S Harris, Nicholas T Ingolia, Alan G Hinnebusch
DEAD-box RNA helicases eukaryotic translation initiation factor 4A (eIF4A) and Ded1 promote translation by resolving mRNA secondary structures that impede preinitiation complex (PIC) attachment to mRNA or scanning. Eukaryotic translation initiation factor 4B (eIF4B) is a cofactor for eIF4A but also might function independently of eIF4A. Ribosome profiling of mutants lacking eIF4B or with impaired eIF4A or Ded1 activity revealed that eliminating eIF4B reduces the relative translational efficiencies of many more genes than does inactivation of eIF4A, despite comparable reductions in bulk translation, and few genes display unusually strong requirements for both factors...
September 20, 2016: Proceedings of the National Academy of Sciences of the United States of America
Hassan Ramshini, Benedetta Mannini, Kaveh Khodayari, Azadeh Ebrahim-Habibi, Azam Sadat Moghaddasi, Reza Tayebee, Fabrizio Chiti
Amyloid or similar protein aggregates are the hallmarks of many disorders, including Alzheimer's, Parkinson's, Huntington's diseases and amyloidoses. The inhibition of the formation of these aberrant species by small molecules is a promising strategy for disease treatment. However, at present, all such diseases lack an appropriate therapeutic approach based on small molecules. In this work we have evaluated five bis(indolyl)phenylmethane derivatives to reduce amyloid fibril formation by hen egg white lysozyme (HEWL) and its associated cytotoxicity...
August 26, 2016: European Journal of Medicinal Chemistry
Sumaiya Iqbal, Md Tamjidul Hoque
A set of features computed from the primary amino acid sequence of proteins, is crucial in the process of inducing a machine learning model that is capable of accurately predicting three-dimensional protein structures. Solutions for existing protein structure prediction problems are in need of features that can capture the complexity of molecular level interactions. With a view to this, we propose a novel approach to estimate position specific estimated energy (PSEE) of a residue using contact energy and predicted relative solvent accessibility (RSA)...
2016: PloS One
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