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 The Core and Holoenzyme Forms of RNA Polymerase from Mycobacterium smegmatis

2018 ◽  
Vol 201 (4) ◽  
Author(s):  
Tomáš Kouba ◽  
Jiří Pospíšil ◽  
Jarmila Hnilicová ◽  
Hana Šanderová ◽  
Ivan Barvík ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Rna Polymerase ◽  
Conformational Changes ◽  
Mycobacterium Smegmatis ◽  
Drug Target ◽  
Conformational Dynamics ◽  
Three Dimensional ◽  
Cryo Electron Microscopy ◽  
Bacterial Rna ◽  
High Degree

ABSTRACT Bacterial RNA polymerase (RNAP) is essential for gene expression and as such is a valid drug target. Hence, it is imperative to know its structure and dynamics. Here, we present two as-yet-unreported forms of Mycobacterium smegmatis RNAP: core and holoenzyme containing σA but no other factors. Each form was detected by cryo-electron microscopy in two major conformations. Comparisons of these structures with known structures of other RNAPs reveal a high degree of conformational flexibility of the mycobacterial enzyme and confirm that region 1.1 of σA is directed into the primary channel of RNAP. Taken together, we describe the conformational changes of unrestrained mycobacterial RNAP. IMPORTANCE We describe here three-dimensional structures of core and holoenzyme forms of mycobacterial RNA polymerase (RNAP) solved by cryo-electron microscopy. These structures fill the thus-far-empty spots in the gallery of the pivotal forms of mycobacterial RNAP and illuminate the extent of conformational dynamics of this enzyme. The presented findings may facilitate future designs of antimycobacterial drugs targeting RNAP.

scholarly journals Divergences in the control of mitochondrial respiration are associated with lifespan variation in marine bivalves

2020 ◽  
Author(s):  
Enrique Rodríguez ◽  
Mohammed Hakkou ◽  
Tory M Hagen ◽  
Hélène Lemieux ◽  
Pierre U Blier
Keyword(s):  
Oxidative Stress ◽  
Electron Transfer ◽  
Complex Iii ◽  
Control Analysis ◽  
Transfer System ◽  
Complex Iv ◽  
Flux Control ◽  
Electron Transfer System ◽  
Marine Bivalves ◽  
Strong Control

Abstract The role played by mitochondrial function in the aging process has been a subject of intense debate in the past few decades, as part of the efforts to understand the mechanistic basis of longevity. The mitochondrial oxidative stress theory of aging (MOSTA) suggests that a progressive decay of this organelle’s function leads to an exacerbation of oxidative stress, with deleterious impact on mitochondrial structure and DNA, ultimately promoting aging. Among the traits suspected to be associated with longevity is the variation in regulation of oxidative phosphorylation, potentially impacting the management of oxidative stress. Longitudinal studies using the framework of metabolic control analysis have shown age-related differences in flux control of respiration, but this approach has seldom been taken on a comparative scale. Using four species of marine bivalves exhibiting a large range of maximum lifespans (from 28y to 507y), we report lifespan-related differences in flux control at different steps of the electron transfer system. Increased longevity was characterized by a lower control by NADH- (complex I-linked) and Succinate- (complex II- linked) pathways, while respiration was strongly controlled by complex IV when compared to shorter-lived species. Complex III exterted a strong control over respiration in all species. Furthermore, high longevity was associated with higher citrate synthase activity, and lower ATP synthase activity. Relieving the control exerted by the electron entry pathways could be advantageous for reaching a higher longevity, leading to an increased control by complex IV, the final electron acceptor in the electron transfer system.

scholarly journals Activation mechanism of human soluble guanylate cyclase by stimulators and activators

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Rui Liu ◽  
Yunlu Kang ◽  
Lei Chen
Keyword(s):  
Electron Microscopy ◽  
Guanylate Cyclase ◽  
Drug Target ◽  
Soluble Guanylate Cyclase ◽  
Activation Mechanism ◽  
Active Conformation ◽  
Cryo Electron Microscopy ◽  
Human Soluble Guanylate Cyclase ◽  
Structural Mechanisms ◽  
Sgc Stimulators

AbstractSoluble guanylate cyclase (sGC) is the receptor for nitric oxide (NO) in human. It is an important validated drug target for cardiovascular diseases. sGC can be pharmacologically activated by stimulators and activators. However, the detailed structural mechanisms, through which sGC is recognized and positively modulated by these drugs at high spacial resolution, are poorly understood. Here, we present cryo-electron microscopy structures of human sGC in complex with NO and sGC stimulators, YC-1 and riociguat, and also in complex with the activator cinaciguat. These structures uncover the molecular details of how stimulators interact with residues from both β H-NOX and CC domains, to stabilize sGC in the extended active conformation. In contrast, cinaciguat occupies the haem pocket in the β H-NOX domain and sGC shows both inactive and active conformations. These structures suggest a converged mechanism of sGC activation by pharmacological compounds.

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 Mutations in the Membrane Anchor of Yeast Cytochrome c1 Compensate for the Absence of Oxa1p and Generate Carbonate-Extractable Forms of Cytochrome c1

Genetics ◽  
1998 ◽  
Vol 150 (2) ◽  
pp. 601-611
Author(s):  
Patrice Hamel ◽  
Claire Lemaire ◽  
Nathalie Bonnefoy ◽  
Paule Brivet-Chevillotte ◽  
Geneviève Dujardin
Keyword(s):  
Electron Transfer ◽  
Complex Iii ◽  
Membrane Anchor ◽  
Suppressor Activity ◽  
Complex Iv ◽  
Transfer Activity ◽  
Suppressor Function ◽  
Mitochondrial Inner Membrane ◽  
Cytochrome C1 ◽  
Inner Membrane Protein

Abstract Oxa1p is a mitochondrial inner membrane protein that is mainly required for the insertion/assembly of complex IV and ATP synthase and is functionally conserved in yeasts, humans, and plants. We have isolated several independent suppressors that compensate for the absence of Oxa1p. Molecular cloning and sequencing reveal that the suppressor mutations (CYT1-1 to -6) correspond to amino acid substitutions that are all located in the membrane anchor of cytochrome c1 and decrease the hydrophobicity of this anchor. Cytochrome c1 is a catalytic subunit of complex III, but the CYT1-1 mutation does not seem to affect the electron transfer activity. The double-mutant cyt1-1,164, which has a drastically reduced electron transfer activity, still retains the suppressor activity. Altogether, these results suggest that the suppressor function of cytochrome c1 is independent of its electron transfer activity. In addition to the membranebound cytochrome c1, carbonate-extractable forms accumulate in all the suppressor strains. We propose that these carbonate-extractable forms of cytochrome c1 are responsible for the suppressor function by preventing the degradation of the respiratory complex subunits that occur in the absence of Oxa1p.

scholarly journals Proposal of a Facile Method to Fabricate a Multi-Dope Multiwall Carbon Nanotube as a Metal-Free Electrocatalyst for the Oxygen Reduction Reaction

2022 ◽  
Vol 14 (2) ◽  
pp. 965
Author(s):  
Sara Bakhtavar ◽  
Mehdi Mehrpooya ◽  
Mahboobeh Manoochehri ◽  
Mehrnoosh Karimkhani
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Electron Transfer ◽  
Low Temperature ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Multiwall Carbon Nanotube ◽  
Multiwall Carbon

In this study, a one-pot, low-temperature synthesis method is considered for the fabrication of heteroatom dope multiwall carbon nanotubes (MWCNT). Doped MWCNT is utilized as an effective electrocatalyst for oxygen reduction reaction (ORR). Single, double, and triple doping of boron, nitrogen and sulfur elements are utilized as the dopants. A reflux system with temperature of 180 °C is implemented in the doping procedure. Actually, unlike the previous studies in which doping on the carbon structures was performed using a furnace at temperatures above 700 °C, in this green and sustainable method, the triple doping on MWCNT is conducted at atmospheric pressure and low temperature. The morphology and structure of the fabricated catalysts were evaluated by Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Raman spectroscopy. According to the results, the nanoparticles were encapsulated in the carbon nanotubes. Aggregated clusters of the sulfur in the case of S-MWCNT are considerable. Cyclic voltammetry (CV), rotating disk electrode, linear sweep voltammetry (LSV), and chronoamperometry electrochemical tests are employed for assessing the oxygen reduction activity of the catalysts. The results illustrate that by using this doping method, the onset potential shifts to positive values towards the oxidized MWCNT. It can be deduced that by doping the N, B, and S atoms on MWCNTs, the defects in the CNT structure, which serve as active sites for ORR application, increase. The N/S/B-doped graphitic layers have a more rapid electron transfer rate at the electrode/electrolyte interface. Thus, this can improve the electrochemistry performance and electron transfer of the MWCNTs. The best performance and electrochemical activity belonged to the NB-MWCNT catalyst (−0.122 V vs. Ag/AgCl). Also, based on the results gained from the Koutecky–Levich (KL) plot, it can be said that the ORR takes place through the 4 e− pathway.

Cytochrome bc1-aa3 oxidase supercomplex as emerging and potential drug target against tuberculosis

2021 ◽  
Vol 14 ◽  
Author(s):  
Thangaraj Sindhu ◽  
Pal Debnath
Keyword(s):  
Drug Target ◽  
Therapeutic Potential ◽  
Complex Iii ◽  
Cytochrome Bc1 ◽  
Cytochrome Bc1 Complex ◽  
Complex Iv ◽  
Transport Chain ◽  
And Function ◽  
Potential Inhibitors ◽  
Role And Function

: The cytochrome bc1-aa3 supercomplex plays an essential role in the cellular respiratory system of Mycobacterium Tuberculosis. It transfers electrons from menaquinol to cytochrome aa3 (Complex IV) via cytochrome bc1 (Complex III), which reduces the oxygen. The electron transfer from a variety of donors into oxygen through the respiratory electron transport chain is essential to pump protons across the membrane creating an electrochemical transmembrane gradient (proton motive force, PMF) that regulates the synthesis of ATP via the oxidative phosphorylation process. Cytochrome bc1-aa3 supercomplex in M. tuberculosis is, therefore, a major drug target for antibiotic action. In recent years, several respiratory chain components have been targeted for developing new candidate drugs, illustrating the therapeutic potential of obstructing energy conversion of M. tuberculosis. The recently available cryo-EM structure of mycobacterial cytochrome bc1-aa3 supercomplex with open and closed conformations has opened new avenues for understanding its structure and function for developing more effective, new therapeutics against pulmonary tuberculosis. In this review, we discuss the role and function of several components, subunits, and drug targeting elements of the supercomplex cytochrome bc1-aa3, and its potential inhibitors in detail.

A light optical diffractometer for electron microscopical images operating in line

1978 ◽  
Vol 36 (1) ◽  
pp. 86-87
Author(s):  
P. Bonhomme ◽  
A. Beorchia
Keyword(s):  
Electron Microscopy ◽  
Electron Transfer ◽  
Electron Microscope ◽  
Image Converter ◽  
Coherent Light ◽  
Spatial Filters ◽  
Electron Image ◽  
Electron Microscopical ◽  
Working Parameters ◽  
Amorphous Part

We have already described (1.2.3) a device using a pockel's effect light valve as a microscopical electron image converter. This converter can be read out with incoherent or coherent light. In the last case we can set in line with the converter an optical diffractometer. Now, electron microscopy developments have pointed out different advantages of diffractometry. Indeed diffractogram of an image of a thin amorphous part of a specimen gives information about electron transfer function and a single look at a diffractogram informs on focus, drift, residual astigmatism, and after standardizing, on periods resolved (4.5.6). These informations are obvious from diffractogram but are usualy obtained from a micrograph, so that a correction of electron microscope parameters cannot be realized before recording the micrograph. Diffractometer allows also processing of images by setting spatial filters in diffractogram plane (7) or by reconstruction of Fraunhofer image (8). Using Electrotitus read out with coherent light and fitted to a diffractometer; all these possibilities may be realized in pseudoreal time, so that working parameters may be optimally adjusted before recording a micrograph or before processing an image.

New challenges to image processing posed by cryo-Electron microscopy of single particles

1991 ◽  
Vol 49 ◽  
pp. 422-423
Author(s):  
Joachim Frank
Keyword(s):  
Electron Microscopy ◽  
Phase Contrast ◽  
Particle Orientation ◽  
Single Particles ◽  
Contrast Transfer Function ◽  
Virtual Absence ◽  
Cryo Electron Microscopy ◽  
Spatial Frequencies ◽  
New Challenges ◽  
Particle Images

Compared with images of negatively stained single particle specimens, those obtained by cryo-electron microscopy have the following new features: (a) higher “signal” variability due to a higher variability of particle orientation; (b) reduced signal/noise ratio (S/N); (c) virtual absence of low-spatial-frequency information related to elastic scattering, due to the properties of the phase contrast transfer function (PCTF); and (d) reduced resolution due to the efforts of the microscopist to boost the PCTF at low spatial frequencies, in his attempt to obtain recognizable particle images.

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