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https://www.readbyqxmd.com/read/27912064/modular-assembly-of-the-bacterial-large-ribosomal-subunit
#1
Joseph H Davis, Yong Zi Tan, Bridget Carragher, Clinton S Potter, Dmitry Lyumkis, James R Williamson
The ribosome is a complex macromolecular machine and serves as an ideal system for understanding biological macromolecular assembly. Direct observation of ribosome assembly in vivo is difficult, as few intermediates have been isolated and thoroughly characterized. Herein, we deploy a genetic system to starve cells of an essential ribosomal protein, which results in the accumulation of assembly intermediates that are competent for maturation. Quantitative mass spectrometry and single-particle cryo-electron microscopy reveal 13 distinct intermediates, which were each resolved to ∼4-5 Å resolution and could be placed in an assembly pathway...
December 1, 2016: Cell
https://www.readbyqxmd.com/read/27912063/structure-of-mammalian-respiratory-supercomplex-i1iii2iv1
#2
Meng Wu, Jinke Gu, Runyu Guo, Yushen Huang, Maojun Yang
The mammalian respiratory chain complexes assemble into supercomplexes (SCs) and reside in the inner mitochondrial membrane to transfer electrons and establish the proton gradient for complex V to synthesize ATP. The precise arrangement of SCs is largely unknown. Here, we report a 4.0-Å cryo-electron microscopy (cryo-EM) structure of the major SC in porcine heart, the 1.7-MDa SCI1III2IV1. The complex III (CIII) dimer and complex IV (CIV) bind at the same side of the L-shaped complex I (CI). Several accessory or supernumerary subunits of CI, such as NDUFA11, NDUFB4, NDUFB8, and NDUFB9, directly contribute to the oligomerization of CI, CIII, and CIV...
December 1, 2016: Cell
https://www.readbyqxmd.com/read/27912062/atomic-structure-of-the-cystic-fibrosis-transmembrane-conductance-regulator
#3
Zhe Zhang, Jue Chen
The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel evolved from the ATP-binding cassette (ABC) transporter family. In this study, we determined the structure of zebrafish CFTR in the absence of ATP by electron cryo-microscopy to 3.7 Å resolution. Human and zebrafish CFTR share 55% sequence identity, and 42 of the 46 cystic-fibrosis-causing missense mutational sites are identical. In CFTR, we observe a large anion conduction pathway lined by numerous positively charged residues...
December 1, 2016: Cell
https://www.readbyqxmd.com/read/27912054/inner-secrets-of-the-respirasome
#4
Andrew Melber, Dennis R Winge
Structure determination by cryo-electron microscopy has approached atomic resolution and helped solve structures of large membrane-protein complexes that resisted crystallography. The 4.0 Å cryo-EM structure of one of the most intricate enzyme systems, the respirasome, in the mitochondrial inner membrane is reported in this issue of Cell.
December 1, 2016: Cell
https://www.readbyqxmd.com/read/27910462/a-precision-cryostat-design-for-manual-and-semi-automated-cryo-plunge-instruments
#5
Christopher J Russo, Steve Scotcher, Martin Kyte
Here we describe a bench-top cryostat system to control the temperature of liquid ethane in a cryo-plunge apparatus designed for biological specimen preparation for electron cryomicroscopy. It comprises a foam insulated Dewar containing a copper cryostat cup, whose temperature is controlled via an active feedback system to within 0.1 K. The device can easily be incorporated into existing manual and semi-automatic cryo-plunge instruments that are not equipped with cryogenic temperature control. Over the course of normal use, we find that using a cryostat is convenient, fast, and does not require special mixtures of cryogens like ethane/propane...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27909983/4-4-%C3%A3-resolution-cryo-em-structure-of-human-mtor-complex-1
#6
Huirong Yang, Jia Wang, Mengjie Liu, Xizi Chen, Min Huang, Dan Tan, Meng-Qiu Dong, Catherine C L Wong, Jiawei Wang, Yanhui Xu, Hong-Wei Wang
Mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) integrates signals from growth factors, cellular energy levels, stress and amino acids to control cell growth and proliferation through regulating translation, autophagy and metabolism. Here we determined the cryo-electron microscopy structure of human mTORC1 at 4.4 Å resolution. The mTORC1 comprises a dimer of heterotrimer (mTOR-Raptor-mLST8) mediated by the mTOR protein. The complex adopts a hollow rhomboid shape with 2-fold symmetry. Notably, mTORC1 shows intrinsic conformational dynamics...
December 1, 2016: Protein & Cell
https://www.readbyqxmd.com/read/27909509/junctional-beats-during-cryo-ablation-of-the-slow-pathway-for-the-elimination-of-atrioventricular-nodal-reentrant-tachycardia
#7
Murat Sucu, Vedat Davutoglu, Esra Polat
The patient was a 39-year-old female with recurrent paroxysmal, regular narrow QRS complex tachycardia. Atrioventricular nodal reentrant tachycardia (AVNRT) was induced. The cryo-ablation attempts (-80°C, 240 second) were performed in the inferior-posterior triangle of Koch. We observed several junctional beats during cryo-ablation. After successful cryo-ablation, AVNRT induction was repeatedly checked during a waiting period of 30 minutes without recurrence. In our case we demonstrated that junctional beats can be observed during cryo-ablation...
June 2016: Journal of Atrial Fibrillation
https://www.readbyqxmd.com/read/27906650/structure-of-the-70s-ribosome-from-human-pathogen-staphylococcus-aureus
#8
Iskander Khusainov, Quentin Vicens, Anthony Bochler, François Grosse, Alexander Myasnikov, Jean-François Ménétret, Johana Chicher, Stefano Marzi, Pascale Romby, Gulnara Yusupova, Marat Yusupov, Yaser Hashem
Comparative structural studies of ribosomes from various organisms keep offering exciting insights on how species-specific or environment-related structural features of ribosomes may impact translation specificity and its regulation. Although the importance of such features may be less obvious within more closely related organisms, their existence could account for vital yet species-specific mechanisms of translation regulation that would involve stalling, cell survival and antibiotic resistance. Here, we present the first full 70S ribosome structure from Staphylococcus aureus, a Gram-positive pathogenic bacterium, solved by cryo-electron microscopy...
October 18, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27906161/structural-basis-for-arfa-rf2-mediated-translation-termination-on-mrnas-lacking-stop-codons
#9
Paul Huter, Claudia Müller, Bertrand Beckert, Stefan Arenz, Otto Berninghausen, Roland Beckmann, Daniel N Wilson
In bacteria, ribosomes stalled on truncated mRNAs lacking a stop codon are rescued by either the transfer-messenger RNA (tmRNA), alternative rescue factor A (ArfA) or ArfB rescue systems(1). While tmRNA- and ArfB-ribosome structures have been elucidated(2-7), structural insight into how ArfA recognizes the presence of truncated mRNAs and recruits the canonical termination release factor RF2 to rescue the stalled ribosomes is lacking. Here we present a cryo-electron microscopy reconstruction of a ribosome stalled on a truncated mRNA in the presence of ArfA and RF2...
December 1, 2016: Nature
https://www.readbyqxmd.com/read/27906160/mechanistic-insights-into-the-alternative-translation-termination-by-arfa-and-rf2
#10
Chengying Ma, Daisuke Kurita, Ningning Li, Yan Chen, Hyouta Himeno, Ning Gao
During cellular translation of mRNAs by ribosomes, various situations that would result in the pausing or stalling of translation apparatus at elongation and termination steps often occur(1-6). Except for programmed stalling, which is usually utilized by the cells to exert regulatory purposes(5,7,8), ribosomes stalled on mRNAs need to be terminated and recycled to maintain adequate cellular translation capacity(9). A large source of ribosome stalling originates in aberrant mRNAs that lack a stop codon. Transcriptional errors and misprocessing of primary transcripts, as well as undesired mRNA cleavage, all contribute to the formation of non-stop mRNAs...
December 1, 2016: Nature
https://www.readbyqxmd.com/read/27905396/atomic-structure-of-the-innexin-6-gap-junction-channel-determined-by-cryo-em
#11
Atsunori Oshima, Kazutoshi Tani, Yoshinori Fujiyoshi
Innexins, a large protein family comprising invertebrate gap junction channels, play an essential role in nervous system development and electrical synapse formation. Here we report the cryo-electron microscopy structures of Caenorhabditis elegans innexin-6 (INX-6) gap junction channels at atomic resolution. We find that the arrangements of the transmembrane helices and extracellular loops of the INX-6 monomeric structure are highly similar to those of connexin-26 (Cx26), despite the lack of significant sequence similarity...
December 1, 2016: Nature Communications
https://www.readbyqxmd.com/read/27902397/vesivirus-2117-capsids-more-closely-resemble-sapovirus-and-lagovirus-particles-than-other-known-vesivirus-structures
#12
Michaela Conley, Edward Emmott, Richard Orton, David Taylor, Daniel Carneiro, Kazuyoshi Murata, Ian Goodfellow, Grant Hansman, David Bhella
Vesivirus 2117 is an adventitious agent that in 2009, was identified as a contaminant of CHO cells propagated in bioreactors at a pharmaceutical manufacturing plant belonging to Genzyme. The consequent interruption in supply of Fabrazyme and Cerezyme (drugs used to treat Fabry and Gaucher disease respectively), caused significant economic losses. Vesivirus 2117 is a member of the Caliciviridae; a family of small icosahedral viruses encoding a positive sense RNA genome. We have used cryo-electron microscopy and three dimensional image reconstruction to calculate a structure of vesivirus 2117 virus like particles as well as feline calicivirus and a chimeric sapovirus...
November 14, 2016: Journal of General Virology
https://www.readbyqxmd.com/read/27900297/effects-of-lymphatic-drainage-and-local-cryo-exposition-regeneration-after-high-intensive-exercises
#13
Michael Behringer, Diana Jedlicka, Molly McCourt, Matthias Ring, Joachim Mester
BACKGROUND: Recovery from exercise and competition is important in sports medicine, particularly when rest periods are short. The objective is to determine the efficacy of cryo exposition (CRY) and manual lymphatic drainage (MLD) to hasten short term recovery of muscle performance after eccentric contractions. METHODS: In a randomized controlled trial, 30 healthy sport students (21 males, 9 females; age: 25.7±2.8 years) performed 4×20 eccentric contractions of knee extensors, followed by 30 min MLD, CRY, or rest (RST) under controlled laboratory environment...
April 2016: Muscles, Ligaments and Tendons Journal
https://www.readbyqxmd.com/read/27899666/structures-of-human-srp72-complexes-provide-insights-into-srp-rna-remodeling-and-ribosome-interaction
#14
Matthias M M Becker, Karine Lapouge, Bernd Segnitz, Klemens Wild, Irmgard Sinning
Co-translational protein targeting and membrane protein insertion is a fundamental process and depends on the signal recognition particle (SRP). In mammals, SRP is composed of the SRP RNA crucial for SRP assembly and function and six proteins. The two largest proteins SRP68 and SRP72 form a heterodimer and bind to a regulatory site of the SRP RNA. Despite their essential roles in the SRP pathway, structural information has been available only for the SRP68 RNA-binding domain (RBD). Here we present the crystal structures of the SRP68 protein-binding domain (PBD) in complex with SRP72-PBD and of the SRP72-RBD bound to the SRP S domain (SRP RNA, SRP19 and SRP68) detailing all interactions of SRP72 within SRP...
November 29, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27899638/structure-and-folding-of-the-tetrahymena-telomerase-rna-pseudoknot
#15
Darian D Cash, Juli Feigon
Telomerase maintains telomere length at the ends of linear chromosomes using an integral telomerase RNA (TER) and telomerase reverse transcriptase (TERT). An essential part of TER is the template/pseudoknot domain (t/PK) which includes the template, for adding telomeric repeats, template boundary element (TBE), and pseudoknot, enclosed in a circle by stem 1. The Tetrahymena telomerase holoenzyme catalytic core (p65-TER-TERT) was recently modeled in our 9 Å resolution cryo-electron microscopy map by fitting protein and TER domains, including a solution NMR structure of the Tetrahymena pseudoknot...
November 29, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27898298/estimation-of-visibility-of-phase-contrast-with-extraction-voltages-for-field-emission-gun-electron-microscopes
#16
Xing Meng
Estimation was made for visibility of phase contrast with varying extraction voltages. The resulting decay rates of visibility show that images with low image contrast from cryo EM will be seriously impacted with high extraction voltages.
November 19, 2016: Ultramicroscopy
https://www.readbyqxmd.com/read/27895910/proteomic-identification-of-cryostress-in-epididymal-spermatozoa
#17
Sung Jae Yoon, Md Saidur Rahman, Woo Sung Kwon, Do Yeal Ryu, Yoo Jin Park, Myung Geol Pang
BACKGROUND: Cryopreservation of epididymal spermatozoa is important in cases in which it is not possible to collect semen using normal methods, as the sudden death of an animal or a catastrophic injury. However, the freezing and thawing processes cause stress to spermatozoa, including cold shock, osmotic damage, and ice crystal formation, thereby reducing sperm quality. We assessed the motility (%), motion kinematics, capacitation status, and viability of spermatozoa using computer-assisted sperm analysis and Hoechst 33258/chlortetracycline fluorescence staining...
2016: Journal of Animal Science and Biotechnology
https://www.readbyqxmd.com/read/27890959/anti-retroviral-therapy-s-miracle-in-the-treatment-of-bowen-s-disease-in-a-human-immunodeficiency-virus-positive-patient-a-rare-case-report
#18
Kannan Gopalan, Seethalakshmi Ganga Vellaisamy, Navakumar Manickam, Razil Ahamed
Bowen's disease (BD) is a form of squamous cell carcinoma in situ often associated with human papillomavirus. Co-infection with human immunodeficiency virus (HIV) is associated with a greater risk of malignancy. We describe a case of BD in a 52-year-old unmarried HIV-positive male who presented with extensive skin lesions of 1-year duration. Histopathology was suggestive of BD. He had been tried with topical imiquimod cream and cryo-therapy for 6 months. We observed no response for these above therapies. He was started on with anti-retroviral therapy (ART) as his CD4 count was 253 cells/mm(3)...
July 2016: Indian Journal of Sexually Transmitted Diseases
https://www.readbyqxmd.com/read/27890922/progress-in-imaging-methods-insights-gained-into-plasmodium-biology
#19
Mariana De Niz, Paul-Christian Burda, Gesine Kaiser, Hernando A Del Portillo, Tobias Spielmann, Freddy Frischknecht, Volker T Heussler
Over the past decade, major advances in imaging techniques have enhanced our understanding of Plasmodium spp. parasites and their interplay with mammalian hosts and mosquito vectors. Cryoelectron tomography, cryo-X-ray tomography and super-resolution microscopy have shifted paradigms of sporozoite and gametocyte structure, the process of erythrocyte invasion by merozoites, and the architecture of Maurer's clefts. Intravital time-lapse imaging has been revolutionary for our understanding of pre-erythrocytic stages of rodent Plasmodium parasites...
November 28, 2016: Nature Reviews. Microbiology
https://www.readbyqxmd.com/read/27890596/monoacyl-phosphatidylcholine-inhibits-the-formation-of-lipid-multilamellar-structures-during-in-vitro-lipolysis-of-self-emulsifying-drug-delivery-systems
#20
Thuy Tran, Scheyla D V S Siqueira, Heinz Amenitsch, Thomas Rades, Anette Müllertz
The colloidal structures formed during lipolysis of self-emulsifying drug delivery systems (SEDDS) might affect the solubilisation and possibly the absorption of drugs. The aim of the current study is to elucidate the structures formed during the in vitro lipolysis of four SEDDS containing medium-chain glycerides and caprylocaproyl polyoxyl-8 glycerides (Labrasol), with or without monoacyl phosphatidylcholine (MAPC). In situ synchrotron small-angle X-ray scattering (SAXS) was combined with ex situ cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) to elucidate the generated structures...
November 23, 2016: European Journal of Pharmaceutical Sciences
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