scholarly journals Molecular basis for the acid initiated uncoating of human enterovirus D68

2018 ◽  
Author(s):  
Yue Liu ◽  
Ju Sheng ◽  
Michael G. Rossmann
Keyword(s):  
Electron Microscopy ◽  
Host Cell ◽  
Common Cold ◽  
Molecular Basis ◽  
Respiratory Infections ◽  
Human Enterovirus ◽  
Structural Rearrangements ◽  
Cryo Electron Microscopy ◽  
Molecular Determinants ◽  
Enterovirus D68

AbstractEnterovirus D68 (EV-D68) belongs to a group of enteroviruses that contain a single positive-sense RNA genome surrounded by an icosahedral capsid. Like common cold viruses, EV-D68 mainly causes respiratory infections and is acid labile. The molecular mechanism by which the acid sensitive EV-D68 virions uncoat and deliver their genome into a host cell is unknown. Using cryo-electron microscopy (cryo-EM), we have determined the structures of the full native virion and an uncoating intermediate (the A(altered)-particle) of EV-D68 at 2.2 Å and 2.7 Å resolution. These structures showed that acid treatment of EV-D68 leads to particle expansion, externalization of the viral protein VP1 N-termini from the capsid interior, and formation of pores around the icosahedral two-fold axes through which the viral RNA can exit. Moreover, because of the low stability of EV-D68 at neutral pH, cryo-EM analyses of a mixed population of particles demonstrated the involvement of multiple structural intermediates during virus uncoating. Among these, a previously undescribed state, the expanded (“E1”) particle, shows a majority of internal regions (e.g, the VP1 N-termini) to be ordered as in the full native virion. Thus, the E1 particle acts as an intermediate in the transition from full native virions to A-particles. Molecular determinants, including a histidine-histidine pair near the two-fold axes, were identified that facilitate this transition under acidic conditions. Thus, the present work delineates the pathway of EV-D68 uncoating and provides the molecular basis for the acid lability of EV-D68 and of the related common cold viruses.Significance StatementEnterovirus D68 (EV-D68) is an emerging pathogen that primarily causes childhood respiratory infections and is linked to neurological diseases. It was unclear how the virus uncoats and delivers its genome into a host cell to establish viral replication. Using high resolution cryo-electron microscopy, we showed that acid induces structural rearrangements of EV-D68 to initiate genome release from the virus. Structural analyses delineated a viral uncoating pathway that involves multiple distinct conformational states. Particularly, the structure of a previously unknown uncoating intermediate enabled the identification of molecular determinants that facilitate EV-D68 uncoating in an acidic environment. These results advance the knowledge of cell entry of EV-D68 and open up possibilities for developing antiviral therapeutics that impede structural rearrangements of the virus.

scholarly journals Molecular basis for the acid-initiated uncoating of human enterovirus D68

2018 ◽  
Vol 115 (52) ◽  
pp. E12209-E12217 ◽  
Author(s):  
Yue Liu ◽  
Ju Sheng ◽  
Arno L. W. van Vliet ◽  
Geeta Buda ◽  
Frank J. M. van Kuppeveld ◽  
...  
Keyword(s):  
Common Cold ◽  
Molecular Basis ◽  
Acid Treatment ◽  
Respiratory Infections ◽  
Human Enterovirus ◽  
Positive Sense ◽  
Single Positive ◽  
Enterovirus D68 ◽  
Icosahedral Capsid ◽  
Acid Labile

Enterovirus D68 (EV-D68) belongs to a group of enteroviruses that contain a single positive-sense RNA genome surrounded by an icosahedral capsid. Like common cold viruses, EV-D68 mainly causes respiratory infections and is acid-labile. The molecular mechanism by which the acid-sensitive EV-D68 virions uncoat and deliver their genome into a host cell is unknown. Using cryoelectron microscopy (cryo-EM), we have determined the structures of the full native virion and an uncoating intermediate [the A (altered) particle] of EV-D68 at 2.2- and 2.7-Å resolution, respectively. These structures showed that acid treatment of EV-D68 leads to particle expansion, externalization of the viral protein VP1 N termini from the capsid interior, and formation of pores around the icosahedral twofold axes through which the viral RNA can exit. Moreover, because of the low stability of EV-D68, cryo-EM analyses of a mixed population of particles at neutral pH and following acid treatment demonstrated the involvement of multiple structural intermediates during virus uncoating. Among these, a previously undescribed state, the expanded 1 (“E1”) particle, shows a majority of internal regions (e.g., the VP1 N termini) to be ordered as in the full native virion. Thus, the E1 particle acts as an intermediate in the transition from full native virions to A particles. Together, the present work delineates the pathway of EV-D68 uncoating and provides the molecular basis for the acid lability of EV-D68 and of the related common cold viruses.

scholarly journals Molecular basis for the ATPase-powered substrate translocation by the Lon AAA+ protease

2020 ◽  
Author(s):  
Kaiming Zhang ◽  
Shanshan Li ◽  
Kan-Yen Hsieh ◽  
Shih-Chieh Su ◽  
Grigore D. Pintilie ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Conformational Changes ◽  
Molecular Basis ◽  
Structural Basis ◽  
Cryo Electron Microscopy ◽  
Adenosine Triphosphatases ◽  
Translocation Mechanism ◽  
Atp Binding And Hydrolysis ◽  
Proteolytic Chamber ◽  
Specific Nucleotide

AbstractThe Lon AAA+ (adenosine triphosphatases associated with diverse cellular activities) protease (LonA) converts ATP-fuelled conformational changes into sufficient mechanical force to drive translocation of the substrate into a hexameric proteolytic chamber. To understand the structural basis for the substrate translocation process, we have determined the cryo-electron microscopy (cryo-EM) structure of Meiothermus taiwanensis LonA (MtaLonA) at 3.6 Å resolution in a substrate-engaged state. Substrate interactions are mediated by the dual pore-loops of the ATPase domains, organized in spiral staircase arrangement from four consecutive protomers in different ATP-binding and hydrolysis states; a closed AAA+ ring is nevertheless maintained by two disengaged ADP-bound protomers transiting between the lowest and highest position. The structure reveals a processive rotary translocation mechanism mediated by LonA-specific nucleotide-dependent allosteric coordination among the ATPase domains, which is induced by substrate binding.

scholarly journals Cryo-EM reveals unique structural features of the FhuCDB Escherichia coli ferrichrome importer

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Wenxin Hu ◽  
Hongjin Zheng
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Molecular Basis ◽  
Iron Uptake ◽  
Structural Features ◽  
Biological Processes ◽  
Type Ii ◽  
Functional Studies ◽  
Cryo Electron Microscopy ◽  
Translocation Pathway

AbstractAs one of the most elegant biological processes developed in bacteria, the siderophore-mediated iron uptake demands the action of specific ATP-binding cassette (ABC) importers. Although extensive studies have been done on various ABC importers, the molecular basis of these iron-chelated-siderophore importers are still not fully understood. Here, we report the structure of a ferrichrome importer FhuCDB from Escherichia coli at 3.4 Å resolution determined by cryo electron microscopy. The structure revealed a monomeric membrane subunit of FhuB with a substrate translocation pathway in the middle. In the pathway, there were unique arrangements of residues, especially layers of methionines. Important residues found in the structure were interrogated by mutagenesis and functional studies. Surprisingly, the importer’s ATPase activity was decreased upon FhuD binding, which deviated from the current understanding about bacterial ABC importers. In summary, to the best of our knowledge, these studies not only reveal a new structural twist in the type II ABC importer subfamily, but also provide biological insights in the transport of iron-chelated siderophores.

scholarly journals Cryo-Electron Microscopy and Biochemical Analysis Offer Insights Into the Effects of Acidic pH, Such as Occur During Acidosis, on the Complement Binding Properties of C-Reactive Protein

2021 ◽  
Vol 12 ◽  
Author(s):  
Dylan P. Noone ◽  
Tijn T. van der Velden ◽  
Thomas H. Sharp
Keyword(s):  
Electron Microscopy ◽  
Biochemical Analysis ◽  
Biochemical Properties ◽  
Structural Basis ◽  
Structural Rearrangements ◽  
C Reactive Protein ◽  
Reactive Protein ◽  
Cryo Electron Microscopy ◽  
Ionic Nature ◽  
The Complement System

The pentraxin family of proteins includes C-reactive protein (CRP), a canonical marker for the acute phase inflammatory response. As compared to normal physiological conditions in human serum, under conditions associated with damage and inflammation, such as acidosis and the oxidative burst, CRP exhibits modulated biochemical properties that may have a structural basis. Here, we explore how pH and ligand binding affect the structure and biochemical properties of CRP. Cryo-electron microscopy was used to solve structures of CRP at pH 7.5 or pH 5 and in the presence or absence of the ligand phosphocholine (PCh), which yielded 7 new high-resolution structures of CRP, including pentameric and decameric complexes. Structures previously derived from crystallography were imperfect pentagons, as shown by the variable angles between each subunit, whereas pentameric CRP derived from cryoEM was found to have C5 symmetry, with subunits forming a regular pentagon with equal angles. This discrepancy indicates flexibility at the interfaces of monomers that may relate to activation of the complement system by the C1 complex. CRP also appears to readily decamerise in solution into dimers of pentamers, which obscures the postulated binding sites for C1. Subtle structural rearrangements were observed between the conditions tested, including a putative change in histidine protonation that may prime the disulphide bridges for reduction and enhanced ability to activate the immune system. Enzyme-linked immunosorbent assays showed that CRP had markedly increased association to the C1 complex and immunoglobulins under conditions associated with acidosis, whilst a reduction in the Ca2+ concentration lowered this pH-sensitivity for C1q, but not immunoglobulins, suggesting different modes of binding. These data suggest a model whereby a change in the ionic nature of CRP and immunological proteins can make it more adhesive to potential ligands without large structural rearrangements.

scholarly journals Cryo-EM structure of the photosynthetic RC-LH1-PufX supercomplex at 2.8-Å resolution

2021 ◽  
Vol 7 (25) ◽  
pp. eabf8864
Author(s):  
Laura Bracun ◽  
Atsushi Yamagata ◽  
Bern M. Christianson ◽  
Tohru Terada ◽  
Daniel P. Canniffe ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electron Transfer ◽  
Molecular Basis ◽  
Bacterial Photosynthesis ◽  
Anoxygenic Photosynthesis ◽  
Light Harvesting Complex ◽  
Cryo Electron Microscopy ◽  
Architectural Features ◽  
Additional Protein ◽  
Large Opening

The reaction center (RC)−light-harvesting complex 1 (LH1) supercomplex plays a pivotal role in bacterial photosynthesis. Many RC-LH1 complexes integrate an additional protein PufX that is key for bacterial growth and photosynthetic competence. Here, we present a cryo–electron microscopy structure of the RC-LH1-PufX supercomplex from Rhodobacter veldkampii at 2.8-Å resolution. The RC-LH1-PufX monomer contains an LH ring of 15 αβ-polypeptides with a 30-Å gap formed by PufX. PufX acts as a molecular “cross brace” to reinforce the RC-LH1 structure. The unusual PufX-mediated large opening in the LH1 ring and defined arrangement of proteins and cofactors provide the molecular basis for the assembly of a robust RC-LH1-PufX supercomplex and efficient quinone transport and electron transfer. These architectural features represent the natural strategies for anoxygenic photosynthesis and environmental adaptation.

scholarly journals Cryo-EM Structures of a Ferrichrome Importer FhuCDB

2021 ◽  
Author(s):  
Wenxin Hu ◽  
Hongjin Zheng
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Atpase Activity ◽  
Molecular Basis ◽  
Iron Uptake ◽  
Biological Processes ◽  
Type Ii ◽  
Functional Studies ◽  
Cryo Electron Microscopy ◽  
Translocation Pathway

As one of the most elegant biological processes developed in bacteria, the siderophore-mediated iron uptake demands the action of specific ATP-binding cassette (ABC) importers. Although extensive studies have been done on various ABC importers, the molecular basis of these iron-chelated-siderophore importers are still not fully understood. Here, we report the structure of a ferrichrome importer FhuCDB from Escherichia coli at 3.4 angstrom resolution determined by cryo electron microscopy. The structure revealed a monomeric membrane subunit of FhuB with a substrate translocation pathway in the middle. In the pathway, there were unique arrangements of residues, especially layers of methionines. Important residues found in the structure were interrogated by mutagenesis and functional studies. Surprisingly, the ATPase activity of the importer was decreased upon FhuD binding, which deviated from the current understanding about bacterial ABC importers. In summary, our studies not only reveal a new structural twist in the type II ABC importer subfamily, but also provide biological insights in the transport of iron-chelated siderophores.

scholarly journals Acute flaccid paralysis following enterovirus D68 associated pneumonia, France, 2014

2014 ◽  
Vol 19 (44) ◽  
Author(s):  
M Lang ◽  
A Mirand ◽  
N Savy ◽  
C Henquell ◽  
S Maridet ◽  
...  
Keyword(s):  
United States ◽  
Neurological Disease ◽  
Acute Flaccid Paralysis ◽  
Respiratory Infections ◽  
The United States ◽  
Flaccid Paralysis ◽  
Human Enterovirus ◽  
Enterovirus D68

Human enterovirus D68 (EV-D68) is known to be associated with mild to severe respiratory infections. Recent reports in the United States and Canada of acute flaccid paralysis (AFP) in children with detection of EV-D68 in respiratory samples have raised concerns about the aetiological role of this EV type in severe neurological disease. This case study is the first report of AFP following EV-D68 infection in Europe.

scholarly journals Convergent Allostery in Ribonucleotide Reductase

2018 ◽  
Author(s):  
William C. Thomas ◽  
F. Phil Brooks ◽  
Audrey A. Burnim ◽  
John-Paul Bacik ◽  
JoAnne Stubbe ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Ribonucleotide Reductase ◽  
Molecular Basis ◽  
Model Organism ◽  
Activity Regulation ◽  
X Ray ◽  
X Ray Scattering ◽  
Cryo Electron Microscopy ◽  
Ribonucleotide Reductases ◽  
Class Ib

AbstractRibonucleotide reductases (RNRs) use a conserved radical-based mechanism to catalyze the conversion of ribonucleotides to deoxyribonucleotides. Within the RNR family, class Ib RNRs are notable for being largely restricted to bacteria, including many pathogens, and for lacking an evolutionarily mobile ATP-cone domain that allosterically controls overall activity. In this study, we report the emergence of a new and unexpected mechanism of activity regulation in the sole RNR of the model organism Bacillus subtilis. Using a hypothesis-driven structural approach that combines the strengths of small-angle X-ray scattering (SAXS), crystallography, and cryo-electron microscopy (cryo-EM), we describe the reversible interconversion of six unique structures, including a flexible, active tetramer and two novel, inhibited filaments. These structures reveal the conformational gymnastics necessary for RNR activity and the molecular basis for its control via an evolutionarily convergent form of allostery.

scholarly journals Cryo-EM structure of adenovirus type 3 fibre with desmoglein 2 shows a novel mode of receptor engagement

2018 ◽  
Author(s):  
Emilie Vassal-Stermann ◽  
Gregory Effantin ◽  
Chloe Zubieta ◽  
Wim Burmeister ◽  
Frédéric Iseni ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Host Cell ◽  
Adenoviral Vector ◽  
Human Adenovirus ◽  
Adenovirus Type ◽  
Adenovirus Infection ◽  
Critical Step ◽  
Cryo Electron Microscopy ◽  
Type 3

AbstractAttachment of adenovirus (HAd) to host cell is a critical step of infection. This work reports the cryo-electron microscopy (cryo-EM) structure of a non-symmetrical complex smaller than 100kDa formed by the trimeric human adenovirus of type 3 fibre knob (HAd3K) and human desmoglein 2 (DSG2). The structure reveals a unique stoichiometry, shedding light to new adenovirus infection strategies and providing new insights for adenoviral vector development.

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