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Protein Science: a Publication of the Protein Society

Kazuhide Miyamoto, Airi Uechi, Kazuki Saito
Human RING finger protein 141 (RFP141) is a germ cell-specific transcription factor during spermatogenesis. We synthesized a compact construct encoding the C-terminal zinc finger of RFP141 (RFP141C peptide). Herein we determined the solution structure of the RFP141C peptide by nuclear magnetic resonance (NMR). Moreover, NMR data and the chemical modification of cysteine residues demonstrated that the RFP141C peptide binds to two zinc atoms in a cross-brace arrangement. The Simple Modular Architecture Research Tool database predicted the structure of RFP141C as a RING finger...
May 25, 2017: Protein Science: a Publication of the Protein Society
Reinhard Grisshammer
Three-dimensional structure determination of integral membrane proteins has advanced in unprecedented detail our understanding of mechanistic events of how ion channels, transporters, receptors and enzymes function. This exciting progress required a tremendous amount of methods development, as exemplified here with G protein-coupled receptors (GPCRs): Optimizing the production of GPCRs in recombinant hosts; increasing the probability of crystal formation using high-affinity ligands, nanobodies, and minimal G proteins for co-crystallization, thus stabilizing receptors into one conformation; using the T4 lysozyme technology and other fusion partners to promote crystal contacts; advancing crystallization methods including the development of novel detergents, and miniaturization and automation of the lipidic cubic phase crystallization method; the concept of conformational thermostabilization of GPCRs; and developing microfocus X-ray synchrotron technologies to analyze small GPCR crystals...
May 25, 2017: Protein Science: a Publication of the Protein Society
Emma L Summers, Mathew H Cumming, Tifany Oulavallickal, Nick Roberts, Vickery L Arcus
Extracellular nucleoside triphosphate diphosphohydrolases (NTPDases) are enzymes that hydrolyse extracellular nucleotides to the respective monophosphate nucleotides. In the past 20 years, NTPDases belonging to mammalian, parasitic and prokaryotic domains of life have been discovered, cloned and characterized. We reveal the first structures of NTPDases from the legume plant species Trifolium repens (7WC) and Vigna unguiculata subsp. cylindrica (DbLNP). Four crystal structures of 7WC and DbLNP were determined at resolutions between 1...
May 24, 2017: Protein Science: a Publication of the Protein Society
Jimin Wang
The charge density (CD) distribution of an atom is the difference per unit volume between the positive charge of its nucleus and the distribution of the negative charges carried by the electrons that are associated with it. The CDs of the atoms in macromolecules are responsible for their electrostatic potential (ESP) distributions, which can now be visualized using cryo-electron microscopy at high resolution. CD maps can be recovered from experimental ESP density maps using the negative Laplacian operation...
May 20, 2017: Protein Science: a Publication of the Protein Society
Ariel R Levy, Meital Turgeman, Lada Gevorkyan-Aiapetov, Sharon Ruthstein
Metallochaperones are responsible for shuttling metal ions to target proteins. Thus, a metallochaperone's structure must be sufficiently flexible both to hold onto its ion while traversing the cytoplasm and to transfer the ion to or from a partner protein. Here, we sought to shed light on the structure of Atox1, a metallochaperone involved in the human copper regulation system. Atox1 shuttles copper ions from the main copper transporter, Ctr1, to the ATP7b transporter in the Golgi apparatus. Conventional biophysical tools such as X-ray or NMR cannot always target the various conformational states of metallochaperones, owing to a requirement for crystallography or low sensitivity and resolution...
May 20, 2017: Protein Science: a Publication of the Protein Society
Dan Sjöstrand, Riccardo Diamanti, Camilla A K Lundgren, Benjamin Wiseman, Martin Högbom
Membrane proteins control a large number of vital biological processes and are often medically important - not least as drug targets. However, membrane proteins are generally more difficult to work with than their globular counterparts, and as a consequence comparatively few high-resolution structures are available. In any membrane protein structure project, a lot of effort is usually spent on obtaining a pure and stable protein preparation. The process commonly involves the expression of several constructs and homologs, followed by extraction in various detergents...
May 20, 2017: Protein Science: a Publication of the Protein Society
Jordan L Woehl, Kasra X Ramyar, Benjamin B Katz, John K Walker, Brian V Geisbrecht
The extracellular adherence protein (Eap) plays a crucial role in pathogenesis and survival of Staphylococcus aureus by inhibiting the classical and lectin pathways of complement. We have previously shown that Eap binds with nanomolar affinity to complement C4b and disrupts the initial interaction between C4b and C2, thereby inhibiting formation of the classical and lectin pathway C3 pro-convertase. Although an underlying mechanism has been identified, the structural basis for Eap binding to C4b is poorly understood...
May 16, 2017: Protein Science: a Publication of the Protein Society
William A Hansen, Sagar D Khare
The design of novel metal-ion binding sites along symmetric axes in protein oligomers could provide new avenues for metalloenzyme design, construction of protein-based nanomaterials and novel ion transport systems. Here, we describe a computational design method, Symmetric Protein Recursive Ion-cofactor Sampling (SyPRIS), for locating constellations of backbone positions within oligomeric protein structures that are capable of supporting desired symmetrically coordinated metal ion(s) chelated by sidechains (chelant model)...
May 15, 2017: Protein Science: a Publication of the Protein Society
M Senissar, M C Manav, D E Brodersen
The PIN (PilT N-terminus) domain is a compact RNA-binding protein domain present in all domains of life. This 120-residue domain consists of a central and parallel β sheet surrounded by α helices, which together organize 4-5 acidic residues in an active site that binds one or more divalent metal ions and in many cases has endoribonuclease activity. In bacteria and archaea, the PIN domain is primarily associated with toxin-antitoxin loci, consisting of a toxin (the PIN domain nuclease) and an antitoxin that inhibits the function of the toxin under normal growth conditions...
May 15, 2017: Protein Science: a Publication of the Protein Society
Baldeep Khare, Sthanam Vl Narayana
Successful adherence, colonization, and survival of Gram-positive bacteria require surface proteins, and multi-protein assemblies called pili. These surface appendages are attractive pharmacotherapeutic targets and understanding their assembly mechanisms is essential for identifying a new class of 'anti-infectives' that do not elicit microbial resistance. Molecular details of the Gram-negative pilus assembly are available in-depth, but the Gram-positive pilus biogenesis is still an emerging field and investigations continue to reveal novel insights into this process...
May 10, 2017: Protein Science: a Publication of the Protein Society
Arjun Prabhakar, Junhong Choi, Jinfan Wang, Alexey Petrov, Joseph D Puglisi
As the universal machine that transfers genetic information from RNA to protein, the ribosome synthesizes proteins with remarkably high fidelity and speed. This is a result of the accurate and efficient decoding of mRNA codons via multistep mechanisms during elongation and termination stages of translation. These mechanisms control how the correct sense codon is recognized by a tRNA for peptide elongation, how the next codon is presented to the decoding center without change of frame during translocation, and how the stop codon is discriminated for timely release of the nascent peptide...
May 8, 2017: Protein Science: a Publication of the Protein Society
Kaixian Liu, Joseph E Rehfus, Elliot Mattson, Christian Kaiser
Correct folding is a prerequisite for the biological activity of most proteins. Folding has largely been studied using in vitro refolding assays with isolated small, robustly folding proteins. A substantial fraction of all cellular proteomes is composed of multi-domain proteins that are often not amenable to this approach, and their folding remains poorly understood. These large proteins likely begin to fold during their synthesis by the ribosome, a large molecular machine that translates the genetic code. The ribosome affects how folding proceeds, but the underlying mechanisms remain largely obscure...
May 5, 2017: Protein Science: a Publication of the Protein Society
Samar Hodeib, Saurabh Raj, M Manosas, Weiting Zhang, Debjani Bagchi, Bertrand Ducos, Francesca Fiorini, Joanne Kanaan, Hervé Le Hir, Jean-François Allemand, David Bensimon, Vincent Croquette
Helicases are a broad family of enzymes that separate nucleic acid double strand structures (DNA/DNA, DNA/RNA or RNA/RNA) and thus are essential to DNA replication and the maintenance of nucleic acid integrity. We review the picture that has emerged from single molecule studies of the mechanisms of DNA and RNA helicases and their interactions with other proteins. Many features have been uncovered by these studies that were obscured by bulk studies, such as DNA strands switching, mechanical (rather than biochemical) coupling between helicases and polymerases, helicase-induced re-hybridization and stalled fork rescue...
May 5, 2017: Protein Science: a Publication of the Protein Society
Xian Hu, Felix Margadant, Mingxi Yao, Michael Sheetz
For individual cells in tissues to create the diverse forms of biological organisms, it is necessary that they must reliably sense and generate the correct forces over the correct distances and directions. There is considerable evidence that the mechanical aspects of the cellular microenvironment provide critical physical parameters to be sensed. How proteins sense forces and cellular geometry to create the correct morphology is not understood in detail but protein unfolding appears to be a major component in force and displacement sensing...
May 5, 2017: Protein Science: a Publication of the Protein Society
Yu Qiu, Yumei Zheng, Kuen-Phon Wu, Brenda A Schulman
Members of the LC3/GABARAP family of ubiquitin-like proteins function during autophagy by serving as membrane linked protein-binding platforms. Their C-termini are physically attached to membranes through covalent linkage to primary amines on lipids such as phosphatidylethanolamine, while their ubiquitin-like fold domains bind "LIR" (LC3-Interacting Region) sequences found within an extraordinarily diverse array of proteins including regulators of autophagy, adaptors that recruit ubiquitinated cargoes to be degraded, and even proteins controlling processes at membranes that are not associated with autophagy...
May 3, 2017: Protein Science: a Publication of the Protein Society
Alexander Minges, Astrid Höppner, Georg Groth
Pyruvate phosphate dikinase (PPDK) is an essential enzyme of both the C4 photosynthetic pathway and cellular energy metabolism of some bacteria and unicellular protists. In C4 plants, it catalyzes the ATP- and Pi-dependent formation of phosphoenolpyruvate (PEP) while in bacteria and protozoa the ATP-forming direction is used. PPDK is composed out of three distinct domains and exhibits one of the largest single domain movements known today during its catalytic cycle. However, little information about potential intermediate steps of this movement were available...
May 3, 2017: Protein Science: a Publication of the Protein Society
Tomomitsu Hatakeyama, Ayaka Ichise, Hideaki Unno, Shuichiro Goda, Tatsuya Oda, Hiroaki Tateno, Jun Hirabayashi, Hitomi Sakai, Hideyuki Nakagawa
The globiferous pedicellariae of the venomous sea urchin Toxopneustes pileolus contains several biologically active proteins. We have cloned the cDNA of one of the toxin components, SUL-I, which is a rhamnose-binding lectin that acts as a mitogen through binding to carbohydrate chains on target cells. Recombinant SUL-I (rSUL-I) was produced in Escherichia coli cells, and its carbohydrate-binding specificity was examined with the glycoconjugate microarray analysis, which suggested that potential target carbohydrate structures are galactose-terminated N-glycans...
May 3, 2017: Protein Science: a Publication of the Protein Society
M Marchetti, A Malinowska, I Heller, Gijs J L Wuite
RNA polymerase (RNAP) is the central motor of gene expression since it governs the process of transcription. In prokaryotes, this holoenzyme is formed by the RNAP core and a sigma factor. After approaching and binding the specific promoter site on the DNA, the holoenzyme-promoter complex undergoes several conformational transitions that allow unwinding and opening of the DNA duplex. Once the first DNA basepairs (∼10bp) are transcribed in an initial transcription process, the enzyme unbinds from the promoter and proceeds downstream along the DNA while continuously opening the helix and polymerizing the ribonucleotides in correspondence with the template DNA sequence...
May 3, 2017: Protein Science: a Publication of the Protein Society
Jingheng Wang, Dorothy Beckett
Class II bifunctional biotin protein ligases (BirA), which catalyze post-translational biotinylation and repress transcription initiation, are broadly distributed in eubacteria and archaea. However, it is unclear if these proteins all share the same molecular mechanism of transcription regulation. In Escherichia coli the corepressor biotinoyl-5'-AMP (bio-5'-AMP), which is also the intermediate in biotin transfer, promotes operator binding and resulting transcription repression by enhancing BirA dimerization...
May 2, 2017: Protein Science: a Publication of the Protein Society
Miriam P Kötzler, Lawrence P McIntosh, Stephen G Withers
Xylanases are important polysaccharide-cleaving catalysts for the pulp and paper, animal feeds and biofuels industries. They have also proved to be valuable model systems for understanding enzymatic catalysis, with one of the best studied being the GH11 xylanase from Bacillus circulans (Bcx). However, proteins from this class are very recalcitrant to refolding in vitro. This both limits their high level expression in heterologous hosts, and prevents experimental approaches, such as peptide ligation or chemical modifications, to probe and engineer their stability and function...
May 2, 2017: Protein Science: a Publication of the Protein Society
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