scholarly journals The two roles of complex III in plants

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Hans-Peter Braun
Keyword(s):  
Complex Iii ◽  
Mitochondrial Enzyme ◽  
Multiple Functions ◽  
Atomic Structures ◽  
Mitochondrial Enzyme Complexes ◽  
Enzyme Complexes

Atomic structures of mitochondrial enzyme complexes in plants are shedding light on their multiple functions.

scholarly journals Function of the maize mitochondrial chaperonin hsp60: specific association between hsp60 and newly synthesized F1-ATPase alpha subunits.

1990 ◽  
Vol 10 (8) ◽  
pp. 3979-3986 ◽  
Author(s):  
T K Prasad ◽  
E Hack ◽  
R L Hallberg
Keyword(s):  
Nuclear Genes ◽  
Mitochondrial Matrix ◽  
F1 Atpase ◽  
Isolated Mitochondria ◽  
Multicomponent Complex ◽  
Mitochondrial Enzyme Complexes ◽  
Specific Association ◽  
Stable Association ◽  
Immunological Assays ◽  
Enzyme Complexes

Mitochondria contain a protein, hsp60, that is induced by heat shock and has been shown to function as a chaperonin in the assembly of mitochondrial enzyme complexes composed of proteins encoded by nuclear genes and imported from the cytosol. To determine whether products of mitochondrial genes are also assembled through an interaction with hsp60, we looked for association between hsp60 and proteins synthesized by isolated mitochondria. We have determined by electrophoretic, centrifugal, and immunological assays that at least two of those proteins become physically associated with hsp60. In mitochondrial matrix extracts, this association could be disrupted by the addition of Mg-ATP. One of the proteins that formed a stable association with hsp60 was the alpha subunit of the multicomponent complex F1-ATPase. We have not identified the other protein. These results indicate that hsp60 can function in the folding and assembly of mitochondrial proteins encoded by both mitochondrial and nuclear genes.

scholarly journals Atomic structures of respiratory complex III2, complex IV, and supercomplex III2-IV from vascular plants

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Maria Maldonado ◽  
Fei Guo ◽  
James A Letts
Keyword(s):  
Vascular Plants ◽  
Proton Translocation ◽  
Complex Iii ◽  
Conformational Heterogeneity ◽  
Mitochondrial Matrix ◽  
Mitochondrial Complex ◽  
Complex Iv ◽  
Atomic Structures ◽  
Iron Sulfur ◽  
Heterogeneity Analysis

Mitochondrial complex III (CIII2) and complex IV (CIV), which can associate into a higher-order supercomplex (SC III2+IV), play key roles in respiration. However, structures of these plant complexes remain unknown. We present atomic models of CIII2, CIV, and SC III2+IV from Vigna radiata determined by single-particle cryoEM. The structures reveal plant-specific differences in the MPP domain of CIII2 and define the subunit composition of CIV. Conformational heterogeneity analysis of CIII2 revealed long-range, coordinated movements across the complex, as well as the motion of CIII2’s iron-sulfur head domain. The CIV structure suggests that, in plants, proton translocation does not occur via the H channel. The supercomplex interface differs significantly from that in yeast and bacteria in its interacting subunits, angle of approach and limited interactions in the mitochondrial matrix. These structures challenge long-standing assumptions about the plant complexes and generate new mechanistic hypotheses.

Function of the maize mitochondrial chaperonin hsp60: specific association between hsp60 and newly synthesized F1-ATPase alpha subunits

1990 ◽  
Vol 10 (8) ◽  
pp. 3979-3986
Author(s):  
T K Prasad ◽  
E Hack ◽  
R L Hallberg
Keyword(s):  
Nuclear Genes ◽  
Mitochondrial Matrix ◽  
F1 Atpase ◽  
Isolated Mitochondria ◽  
Multicomponent Complex ◽  
Mitochondrial Enzyme Complexes ◽  
Specific Association ◽  
Stable Association ◽  
Immunological Assays ◽  
Enzyme Complexes

Mitochondria contain a protein, hsp60, that is induced by heat shock and has been shown to function as a chaperonin in the assembly of mitochondrial enzyme complexes composed of proteins encoded by nuclear genes and imported from the cytosol. To determine whether products of mitochondrial genes are also assembled through an interaction with hsp60, we looked for association between hsp60 and proteins synthesized by isolated mitochondria. We have determined by electrophoretic, centrifugal, and immunological assays that at least two of those proteins become physically associated with hsp60. In mitochondrial matrix extracts, this association could be disrupted by the addition of Mg-ATP. One of the proteins that formed a stable association with hsp60 was the alpha subunit of the multicomponent complex F1-ATPase. We have not identified the other protein. These results indicate that hsp60 can function in the folding and assembly of mitochondrial proteins encoded by both mitochondrial and nuclear genes.

Characterization by X-ray powder diffraction of alpha lipoic acid

2016 ◽  
Vol 32 (1) ◽  
pp. 35-39
Author(s):  
Jose H. Quintana Mendoza ◽  
R. A. Toro ◽  
Laura A. Blanco ◽  
J. A. Henao
Keyword(s):  
Powder Diffraction ◽  
Lipoic Acid ◽  
Alpha Lipoic Acid ◽  
Monoclinic Crystal ◽  
Cell Parameters ◽  
Mitochondrial Enzyme Complexes ◽  
Specific Proteins ◽  
Structural Database ◽  
Enzyme Complexes

Alpha lipoic acid (ALA) C8H14O2S2 is a naturally occurring compound that is synthesized in small amounts by plants and animals, including humans. ALA is covalently bound to specific proteins, which function as cofactors for several important mitochondrial enzyme complexes and studies suggest that they might help with type 2 diabetes. In the Cambridge Structural Database, there are four entries related to this compound: two for lipoic acid and two for complexes. In the Powder Diffraction File-4, two experimental unindexed patterns are reported. The material crystallizes in a monoclinic crystal system, space group P21/a and cell parameters a = 9.237 (1) Å, b = 9.960 (1) Å, c = 11.787 (2) Å, β = 109.13 (1)°, and V = 1024.6 (2) Å3.

Mitochondrial complexes I, II, III, IV, and V in myocardial ischemia and autolysis

1983 ◽  
Vol 244 (6) ◽  
pp. H743-H748 ◽  
Author(s):  
W. Rouslin
Keyword(s):  
Myocardial Ischemia ◽  
Oxygen Uptake ◽  
Complex I ◽  
Complex Iii ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Anesthetized Dogs ◽  
Activity Loss ◽  
Enzyme Complexes

Ischemic myocardium was produced by occluding the left circumflex coronary artery in anesthetized dogs. Autolyzed myocardium was produced by incubating transmural samples of canine left ventricle at 37 degrees C. Tissue pH was recorded continuously in each model using a microcombination pH electrode impaled into the midmyocardium. The activities of the five mitochondrial inner membrane enzyme complexes of electron transport and coupled oxidative phosphorylation were assayed as a function of time of ischemia or autolysis. While the activities of complex II (succinate-CoQ reductase) and IV (cytochrome c oxidase) were completely stable, that of complex I (NADH-CoQ reductase) decreased markedly, but largely only after 20 min of ischemia or autolysis. At 20 min and beyond, the decrease in the activity of complex I paralleled closely the decrease in whole mitochondrial oxygen uptake with NAD-linked substrates in both models. The activity of complex III (CoQH2-c reductase) decreased at a more gradual rate during ischemia or autolysis, and its rate of decrease paralleled that of succinate-supported oxygen uptake. The activity of complex V (oligomycin-sensitive ATPase) decreased most rapidly (by 40% in only 5 min of autolysis) but nearly leveled off beyond 20 min in the two models. A strikingly similar pattern of differential enzyme lability was observed in isolated control mitochondria incubated at lowered pH values. The results demonstrate 1) differential enzyme lability within the mitochondrial inner membrane, 2) a connection between severity of acidosis and the degree of enzyme activity loss, and 3) the usefulness of simple tissue autolysis as an analogue of in situ myocardial ischemia.

scholarly journals Atomic structures of respiratory complex III2, complex IV and supercomplex III2-IV from vascular plants

2020 ◽  
Author(s):  
María Maldonado ◽  
Fei Guo ◽  
James A. Letts
Keyword(s):  
Vascular Plants ◽  
Proton Translocation ◽  
Complex Iii ◽  
Conformational Heterogeneity ◽  
Mitochondrial Matrix ◽  
Mitochondrial Complex ◽  
Complex Iv ◽  
Atomic Structures ◽  
Iron Sulfur ◽  
Heterogeneity Analysis

Mitochondrial complex III (CIII2) and complex IV (CIV), which can associate into a higher-order supercomplex (SC III2+IV), play key roles in respiration. However, structures of these plant complexes remain unknown. We present atomic models of CIII2, CIV and SC III2+IV from Vigna radiata determined by single-particle cryoEM. The structures reveal plant-specific differences in the MPP domain of CIII2 and define the subunit composition of CIV. Conformational heterogeneity analysis of CIII2 revealed long-range, coordinated movements across the complex, as well as the motion of CIII2’s iron-sulfur head domain. The CIV structure suggests that, in plants, proton translocation does not occur via the H-channel. The supercomplex interface differs significantly from that in yeast and bacteria in its interacting subunits, angle of approach and limited interactions in the mitochondrial matrix. These structures challenge long-standing assumptions about the plant complexes, generate new mechanistic hypotheses and allow for the generation of more selective agricultural inhibitors.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

Quasiperiodic interfaces: HREM observations of grain and phase boundaries

1990 ◽  
Vol 48 (4) ◽  
pp. 332-333
Author(s):  
K. L. Merkle
Keyword(s):  
Atomic Structure ◽  
Direct Determination ◽  
Lattice Parameter ◽  
Atomic Scale ◽  
Misfit Dislocations ◽  
Oxide Systems ◽  
Atomic Structures ◽  
Periodic Arrays ◽  
Parameter Ratio ◽  
Metal Metal

The atomic structures of internal interfaces have recently received considerable attention, not only because of their importance in determining many materials properties, but also because the atomic structure of many interfaces has become accessible to direct atomic-scale observation by modem HREM instruments. In this communication, several interface structures are examined by HREM in terms of their structural periodicities along the interface.It is well known that heterophase boundaries are generally formed by two low-index planes. Often, as is the case in many fcc metal/metal and metal/metal-oxide systems, low energy boundaries form in the cube-on-cube orientation on (111). Since the lattice parameter ratio between the two materials generally is not a rational number, such boundaries are incommensurate. Therefore, even though periodic arrays of misfit dislocations have been observed by TEM techniques for numerous heterophase systems, such interfaces are quasiperiodic on an atomic scale. Interfaces with misfit dislocations are semicoherent, where atomically well-matched regions alternate with regions of misfit. When the misfit is large, misfit localization is often difficult to detect, and direct determination of the atomic structure of the interface from HREM alone, may not be possible.

Flux-pinning-related defect structures in melt-processed YBa2Cu3O7-x

1993 ◽  
Vol 51 ◽  
pp. 936-937
Author(s):  
Z. L. Wang ◽  
R. Kontra ◽  
A. Goyal ◽  
D. M. Kroeger ◽  
L.F. Allard
Keyword(s):  
Volume Fraction ◽  
Local Density ◽  
Stacking Faults ◽  
Image Resolution ◽  
Defect Structures ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Point Image ◽  
Related Defect ◽  
Point To Point

Previous studies of Y2BaCuO5/YBa2Cu3O7-δ(Y211/Y123) interfaces in melt-processed and quench-melt-growth processed YBa2Cu3O7-δ using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) have revealed a high local density of stacking faults in Y123, near the Y211/Y123 interfaces. Calculations made using simple energy considerations suggested that these stacking faults may act as effective flux-pinners and may explain the observations of increased Jc with increasing volume fraction of Y211. The present paper is intended to determine the atomic structures of the observed defects. HRTEM imaging was performed using a Philips CM30 (300 kV) TEM with a point-to-point image resolution of 2.3 Å. Nano-probe EDS analysis was performed using a Philips EM400 TEM/STEM (100 kV) equipped with a field emission gun (FEG), which generated an electron probe of less than 20 Å in diameter.Stacking faults produced by excess single Cu-O layers: Figure 1 shows a HRTEM image of a Y123 film viewed along [100] (or [010]).

High-Resolution Image Simulation of a Tilted Crystal

1990 ◽  
Vol 48 (1) ◽  
pp. 68-69
Author(s):  
C. J. D. Hetherington
Keyword(s):  
High Resolution ◽  
Crystal Thickness ◽  
Thin Specimen ◽  
Atomic Structures ◽  
Kikuchi Lines ◽  
High Resolution Images ◽  
Final Estimate ◽  
Simulated Images ◽  
Habit Planes

Most high resolution images are not directly interpretable but must be compared with simulations based on model atomic structures and appropriate imaging conditions. Typically, the only parameters that are adjusted, in addition to the structure models, are crystal thickness and microscope defocus. Small tilts of the crystal away from the exact zone axis have only rarely been considered. It is shown here that, in the analysis of an image of a silicon twin intersection, the crystal tilt could be accurately estimated and satisfactorily included in the simulations.The micrograph shown in figure 1 was taken as part of an HREM study of indentation-induced hexagonal silicon. In this instance, the intersection of two twins on different habit planes has driven the silicon into hexagonal stacking. However, in order to confirm this observation, and in order to investigate other defects in the region, it has been necessary to simulate the image taking into account the very apparent crystal tilt. The inability to orientate the specimen at the exact [110] zone was influenced by i) the buckling of the specimen caused by strains at twin intersections, ii) the absence of Kikuchi lines or a clearly visible Laue circle in the diffraction pattern of the thin specimen and iii) the avoidance of radiation damage (which had marked effects on images taken a few minutes later following attempts to realign the crystal.) The direction of the crystal tilt was estimated by observing which of the {111} planes remained close to edge-on to the beam and hence strongly imaged. Further refinement of the direction and magnitude of the tilt was done by comparing simulated images to experimental images in a through-focal series. The presence of three different orientations of the silicon lattice aided the unambiguous determination of the tilt. The final estimate of a 0.8° tilt in the 200Å thick specimen gives atomic columns a projected width of about 3Å.

Sign in / Sign up

Export Citation Format

Share Document