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.

Structure of the maize photosystem I supercomplex with light-harvesting complexes I and II

Science ◽  
2018 ◽  
Vol 360 (6393) ◽  
pp. 1109-1113 ◽  
Author(s):  
Xiaowei Pan ◽  
Jun Ma ◽  
Xiaodong Su ◽  
Peng Cao ◽  
Wenrui Chang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Energy Transfer ◽  
Complex I ◽  
Light Harvesting ◽  
Light Conditions ◽  
Light Harvesting Complexes ◽  
Light Harvesting Complex ◽  
Cryo Electron Microscopy ◽  
Photosystems I And Ii ◽  
Light Harvesting Complex Ii

Plants regulate photosynthetic light harvesting to maintain balanced energy flux into photosystems I and II (PSI and PSII). Under light conditions favoring PSII excitation, the PSII antenna, light-harvesting complex II (LHCII), is phosphorylated and forms a supercomplex with PSI core and the PSI antenna, light-harvesting complex I (LHCI). Both LHCI and LHCII then transfer excitation energy to the PSI core. We report the structure of maize PSI-LHCI-LHCII solved by cryo–electron microscopy, revealing the recognition site between LHCII and PSI. The PSI subunits PsaN and PsaO are observed at the PSI-LHCI interface and the PSI-LHCII interface, respectively. Each subunit relays excitation to PSI core through a pair of chlorophyll molecules, thus revealing previously unseen paths for energy transfer between the antennas and the PSI core.

scholarly journals Synthetic self-assembling ADDomer platform for highly efficient vaccination by genetically encoded multiepitope display

2019 ◽  
Vol 5 (9) ◽  
pp. eaaw2853 ◽  
Author(s):  
Charles Vragniau ◽  
Joshua C. Bufton ◽  
Frédéric Garzoni ◽  
Emilie Stermann ◽  
Fruzsina Rabi ◽  
...  
Keyword(s):  
Infectious Disease ◽  
Electron Microscopy ◽  
High Performance ◽  
Vaccine Candidate ◽  
Cost Effective ◽  
Atomic Resolution ◽  
Self Assembling ◽  
Cryo Electron Microscopy ◽  
Architectural Features ◽  
Multimeric Protein

Self-assembling virus-like particles represent highly attractive tools for developing next-generation vaccines and protein therapeutics. We created ADDomer, an adenovirus-derived multimeric protein-based self-assembling nanoparticle scaffold engineered to facilitate plug-and-play display of multiple immunogenic epitopes from pathogens. We used cryo–electron microscopy at near-atomic resolution and implemented novel, cost-effective, high-performance cloud computing to reveal architectural features in unprecedented detail. We analyzed ADDomer interaction with components of the immune system and developed a promising first-in-kind ADDomer-based vaccine candidate to combat emerging Chikungunya infectious disease, exemplifying the potential of our approach.

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-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 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 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 An electron transfer path connects subunits of a mycobacterial respiratory supercomplex

Science ◽  
2018 ◽  
Vol 362 (6418) ◽  
pp. eaat8923 ◽  
Author(s):  
Hongri Gong ◽  
Jun Li ◽  
Ao Xu ◽  
Yanting Tang ◽  
Wenxin Ji ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electron Transfer ◽  
Superoxide Dismutase ◽  
Oxygen Reduction ◽  
Mycobacterium Smegmatis ◽  
Drug Target ◽  
Complex Iii ◽  
Complex Iv ◽  
Transfer Path ◽  
Cryo Electron Microscopy

We report a 3.5-angstrom-resolution cryo–electron microscopy structure of a respiratory supercomplex isolated fromMycobacterium smegmatis.It comprises a complex III dimer flanked on either side by individual complex IV subunits. Complex III and IV associate so that electrons can be transferred from quinol in complex III to the oxygen reduction center in complex IV by way of a bridging cytochrome subunit. We observed a superoxide dismutase-like subunit at the periplasmic face, which may be responsible for detoxification of superoxide formed by complex III. The structure reveals features of an established drug target and provides a foundation for the development of treatments for human tuberculosis.

scholarly journals Broad host range of SARS-CoV-2 and the molecular basis for SARS-CoV-2 binding to cat ACE2

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Lili Wu ◽  
Qian Chen ◽  
Kefang Liu ◽  
Jia Wang ◽  
Pengcheng Han ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Intermediate Host ◽  
Molecular Basis ◽  
Binding Mode ◽  
Domestic Animals ◽  
Broad Host Range ◽  
Receptor Binding Domain ◽  
Wild Animals ◽  
Cryo Electron Microscopy ◽  
Shed Light

Abstract Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the recent pandemic COVID-19, is reported to have originated from bats, with its intermediate host unknown to date. Here, we screened 26 animal counterparts of the human ACE2 (hACE2), the receptor for SARS-CoV-2 and SARS-CoV, and found that the ACE2s from various species, including pets, domestic animals and multiple wild animals, could bind to SARS-CoV-2 receptor binding domain (RBD) and facilitate the transduction of SARS-CoV-2 pseudovirus. Comparing to SARS-CoV-2, SARS-CoV seems to have a slightly wider range in choosing its receptor. We further resolved the cryo-electron microscopy (cryo-EM) structure of the cat ACE2 (cACE2) in complex with the SARS-CoV-2 RBD at a resolution of 3 Å, revealing similar binding mode as hACE2 to the SARS-CoV-2 RBD. These results shed light on pursuing the intermediate host of SARS-CoV-2 and highlight the necessity of monitoring susceptible hosts to prevent further outbreaks.

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