Relationships between mitochondrial outer membranes and agranular reticulum in nervous tissue: ultrastructural observations and a new interpretation

1980 ◽  
Vol 46 (1) ◽  
pp. 129-147
Author(s):  
J. Spacek ◽  
A.R. Lieberman
Keyword(s):  
Nervous Tissue ◽  
Mitochondrial Membrane ◽  
Nerve Cells ◽  
Outer Mitochondrial Membrane ◽  
Inner Mitochondrial Membrane ◽  
Thin Sections ◽  
3 Dimensional ◽  
Outer Membranes ◽  
New Interpretation ◽  
In Cells

This study is concerned with extensions of the outer membranes of mitochondria in cells of nervous tissue, and with possible relationships between the extensions and the agranular reticulum. A variety of preparative techniques was applied to a large number of different central nervous tissues (CNS) and peripheral nervous tissues (PNS), using conventional thin sections, thicker sections (100 nm or more) and 3-dimensional reconstructions of serial thin sections. Extensions were commonly observed, particularly from the ends of longitudinally oriented mitochondria in axons and dendrites. Often these had the appearance of, and could be traced into apparent continuity with, adjacent elements of the agranular membrane. In addition to these apical tubular extensions, we also observed and reconstructed short lateral tubular or sac-like extensions and vesicular protrusions of the outer mitochondrial membrane. We discuss and discount the possibility that the extensions are artefacts, consider the structural and biochemical similarities between the outer mitochondrial membrane and agranular reticulum and propose that the outer mitochondrial is part of the agranular reticulum (or a specialized portion of the agranular reticulum). We suggest that the translocation of mitochondria in nerve cells, and probably in other cells as well, involves movement of the inner mitochondrial membrane and the enclosed matrix (mitoplast) within channels of agranular reticulum in continuity, or in transient continuity, with the outer mitochondrial membrane.

Structural cross-bridges between microtubules and mitochondria in central axons of an insect (Periplaneta americana)

1977 ◽  
Vol 27 (1) ◽  
pp. 255-272
Author(s):  
D.S. Smith ◽  
U. Jarlfors ◽  
M.L. Cayer
Keyword(s):  
Electron Micrographs ◽  
Mitochondrial Membrane ◽  
Periplaneta Americana ◽  
Freeze Fracture ◽  
Outer Mitochondrial Membrane ◽  
Thin Sections ◽  
Cross Bridge ◽  
Multiple Association ◽  
Random Models ◽  
Cross Bridges

The distribution of microtubules and mitochondria in central axons of an insect (Periplaneta americana) is assessed by comparison between counts on micrographs and computed axon random ‘models’. These studies show that the observed multiple association of microtubules with individual mitochondria is statistically highly significant. Electron micrographs of thin sections show that linkage is effected by physical cross-bridge, possibly comprising components from the microtubule and mitochondrion. Linear particle arrays are described on the outer mitochondrial membrane in freeze-fracture replicas, and tentatively related to the bridges seen in thin sections. The results are discussed in terms of proposed roles of microtubules in neurons and other cells.

Cytochemical Localization of Transferase Activities: Carnitine Acetyltransferase

1970 ◽  
Vol 6 (1) ◽  
pp. 29-50
Author(s):  
JOAN A. HIGGINS ◽  
R. J. BARRNETT
Keyword(s):  
Mitochondrial Membrane ◽  
Carnitine Acetyltransferase ◽  
Inner Mitochondrial Membrane ◽  
Acetyl Coa ◽  
Cytochemical Localization ◽  
Fixed Tissue ◽  
Structural Localization ◽  
Outer Membranes ◽  
Sh Group ◽  
Ferrocyanide Method

Two methods for the cytochemical detection of free CoA and their utilization in the fine-structural localization of carnitine acetyltransferase in rat heart are described. The first utilizes the reducing property of the SH group of CoA to reduce potassium ferricyanide to potassium ferrocyanide, which in the presence of uranyl ions forms an electron-dense precipitate of uranyl ferrocyanide. The second utilizes the mercaptide-forming property of the free SH group of CoA, which forms a precipitate with cadmium ions. Using the uranyl-ferrocyanide method, reaction product due to endogenous enzymic activity was found on and between the cristae and between the inner and outer membranes of the mitochondria in fresh heart muscle. In aldehyde-fixed tissue activity was recorded only between the inner and outer membranes. Endogenous activity was removed by preincubation of the tissue in a solution of ferricyanide. On addition of acetyl CoA and carnitine to the incubation medium, fresh tissue, which had been preincubated in ferricyanide, showed reaction product between and on the cristae and between the inner and outer membranes of the mitochondria, while fixed tissue showed reaction product in the latter position only. In both cases the activity between the outer and inner mitochondrial membranes was dependent on both acetyl CoA and carnitine, while the cristae reaction occurred in the absence of carnitine, but required acetyl CoA. All activity was inhibited by mercuric chloride. Acetyl carnitine reduced the activity in the fixed tissue and had severe effects on the structure of fresh mitochondria. These results suggest the presence of carnitine acetyltransferase, which survives aldehyde fixation, on the inner surface of the outer mitochondrial membrane and/or the outer surface of the inner mitochondrial membrane. A second enzyme which released CoA from acetyl CoA occurred in relation to the cristae of unfixed mitochondria. The cadmium method was less satisfactory than the uranyl-ferrocyanide method but with fixed tissue gave confirmatory results.

Synthesis of the inner mitochondrial membrane and the intercalation of respiratory enzymes during the cell cycle of Chlorella

1976 ◽  
Vol 21 (2) ◽  
pp. 329-340
Author(s):  
B.G. Forde ◽  
B.E. Gunning ◽  
P.C. John
Keyword(s):  
Cell Cycle ◽  
Succinate Dehydrogenase ◽  
Mitochondrial Membrane ◽  
Extended Period ◽  
Outer Mitochondrial Membrane ◽  
Inner Mitochondrial Membrane ◽  
Chlorella Fusca ◽  
Respiratory Enzymes ◽  
Membrane Area ◽  
Enzyme Molecules

The ratio of inner to outer mitochondrial membrane area remains close to 1–8 throughout the cell cycle in synchronized cells of Chlorella fusca var, vacuolata 211-8p. Using estimates of this ratio, together with our previous estimates of mitochondrial surface area, to calculate the absolute area of inner mitochondrial membrane, it is demonstrated that growth of the inner mitochondrial membrane during the cell cycle occupies an extended period and parallels the growth of the whole cell. In contrast, the synthesis of succinate dehydrogenase and cytochrome oxidase is restricted to the last third of the cell cycle. It is concluded that mitochondrial growth involves the intercalation of periodically synthesized respiratory enzymes into membranes made earlier in the cycle, with consequent 5-fold changes in the density of active enzyme molecules in the membrane. These observations are discussed in relation to the control of mitochondiral membrane synthesis, membrane assembly and respiration rate during the cell cycle.

scholarly journals Molecular mechanism of mitochondrial phosphatidate transfer by Ups1

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Jiuwei Lu ◽  
Chun Chan ◽  
Leiye Yu ◽  
Jun Fan ◽  
Fei Sun ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Mitochondrial Membrane ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Membranes ◽  
Inner Mitochondrial Membrane ◽  
Membrane Interaction ◽  
Detailed Mechanism ◽  
Physiological Regulator ◽  
Membrane Bound ◽  
Dynamics Simulations

AbstractCardiolipin, an essential mitochondrial physiological regulator, is synthesized from phosphatidic acid (PA) in the inner mitochondrial membrane (IMM). PA is synthesized in the endoplasmic reticulum and transferred to the IMM via the outer mitochondrial membrane (OMM) under mediation by the Ups1/Mdm35 protein family. Despite the availability of numerous crystal structures, the detailed mechanism underlying PA transfer between mitochondrial membranes remains unclear. Here, a model of Ups1/Mdm35-membrane interaction is established using combined crystallographic data, all-atom molecular dynamics simulations, extensive structural comparisons, and biophysical assays. The α2-loop, L2-loop, and α3 helix of Ups1 mediate membrane interactions. Moreover, non-complexed Ups1 on membranes is found to be a key transition state for PA transfer. The membrane-bound non-complexed Ups1/ membrane-bound Ups1 ratio, which can be regulated by environmental pH, is inversely correlated with the PA transfer activity of Ups1/Mdm35. These results demonstrate a new model of the fine conformational changes of Ups1/Mdm35 during PA transfer.

Differential staining of crystalline arrays of outer mitochondrial membrane channels

1983 ◽  
Vol 41 ◽  
pp. 444-445
Author(s):  
Carmen A. Mannella ◽  
Joachim Frank
Keyword(s):  
Mitochondrial Membrane ◽  
Differential Staining ◽  
Mitochondrial Outer Membrane ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Channels ◽  
Outer Membranes ◽  
Main Protein ◽  
Protein Components ◽  
Regular Arrays

The mitochondrial outer membrane contains pore-forming polypeptides (Mr⋍= 30,000) which are its main protein components in plants and fungi. Outer membranes (OM) isolated from Neurospora mitochondria often contain extended regular arrays of subunits with stain-accumulating centers 2-3 nm in diameter. That these subunits are the mitochondrial channels has been established immunologically. Antibodies against the predominant 31-kDa OM polypeptide of Neurospora (a) prevent in vitro insertion of OM channels into bilayers and (b) preferentially bind to the crystalline membranes in OM fractions.Planar projections of individual OM channel layers have been reconstructed from electron micrographs of negatively stained crystalline vesicles by Fourier filtration. In the usual array (Fig. 1a) the unit cell is a parallelogram which can hold six stain centers (putative pore openings) arranged in a hexagon with p2 symmetry. There are large pore-free areas in these arrays (* in Fig. 1a) which are likely composed of phospholipid, since they disappear when the membranes are treated with phospholipase A2 (Fig. 1b).

scholarly journals Protease OMA1 Modulates Mitochondrial Bioenergetics and Ultrastructure through Dynamic Association with MICOS Complex

2020 ◽  
Author(s):  
Martonio Ponte Viana ◽  
Roman M. Levytskyy ◽  
Ruchika Anand ◽  
Andreas S. Reichert ◽  
Oleh Khalimonchuk
Keyword(s):  
Mitochondrial Membrane ◽  
Outer Mitochondrial Membrane ◽  
Mitochondrial Ultrastructure ◽  
Mitochondrial Membranes ◽  
Complex Dynamic ◽  
Contact Site ◽  
Outer Membranes ◽  
Mitochondrial Functions ◽  
Membrane Contacts ◽  
Dynamic Association

ABSTRACTRemodeling of mitochondrial ultrastructure is a complex dynamic process that is critical for a variety of mitochondrial functions and apoptosis. Although the key regulators of this process - mitochondrial contact site and cristae junction organizing system (MICOS) and GTPase Optic Atrophy 1 (OPA1) have been characterized, the mechanisms behind this regulation remain incompletely defined. Here, we found that in addition to its role in mitochondrial division, metallopeptidase OMA1 is required for maintenance of contacts between the inner and outer membranes through a dynamic association with MICOS. This association is independent of OPA1, appears to be mediated via the MICOS subunit MIC60, and is important for stability of MICOS machinery and the inner-outer mitochondrial membrane contacts. We find that OMA1-MICOS relay is required for stability of respiratory supercomplexes, optimal bioenergetic output in response to cellular insults, and apoptosis. Loss of OMA1 affects these activities; remarkably it can be partially compensated for by an artificial MICOS-emulating tether protein that bridges the inner and outer mitochondrial membranes. Our data show that OMA1-mediated support of mitochondrial ultrastructure is required for maintenance of mitochondrial architecture and bioenergetics under both basal and homeostasis-challenging conditions, and suggest a previously unrecognized role for this protease in mitochondrial physiology.

scholarly journals Molecular mechanism of mitochondrial phosphatidate transfer by Ups1/Mdm35

2019 ◽  
Author(s):  
Jiuwei Lu ◽  
Kevin Chan ◽  
Leiye Yu ◽  
Jun Fan ◽  
Yujia Zhai ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Conformational Changes ◽  
Transfer Rate ◽  
Mitochondrial Membrane ◽  
Physiological Function ◽  
Bound State ◽  
Outer Mitochondrial Membrane ◽  
Structural Elements ◽  
Inner Mitochondrial Membrane ◽  
Dynamics Simulations

ABSTRACTCardiolipin plays many important roles for mitochondrial physiological function and is synthesized from phosphatidic acid (PA) at inner mitochondrial membrane (IMM). PA synthesized from endoplasmic reticulum needs to transfer to IMM via outer mitochondrial membrane (OMM). The transfer of PA between IMM and OMM is mediated by Ups1/Mdm35 protein family. Although there are many structures of this family available, the detailed molecular mechanism of how PA is transferred between membranes is yet unknown. Here, we report another crystal structures of Ups1/Mdm35 in the authentic monomeric apo state and the DHPA bound state. By combining subsequent all-atom molecular dynamics simulations, extensive structural comparisons and biophysical assays, we discovered the conformational changes of Ups1/Mdm35, identified key structural elements and residues during membrane binding and PA entry. We found the monomeric Ups1 on membrane is an important transit for the success of PA transfer, and the equilibrium between monomeric Ups1 and Ups1/Mdm35 complex on membrane affects the PA transfer rate and can be regulated by many factors including environmental pH.

scholarly journals Phosphatidylethanolamine made in the inner mitochondrial membrane is essential for yeast cytochromebc1complex function

2018 ◽  
Author(s):  
Elizabeth Calzada ◽  
J. Michael McCaffery ◽  
Steven M. Claypool
Keyword(s):  
Mitochondrial Function ◽  
Mitochondrial Membrane ◽  
Complex Iii ◽  
Biosynthetic Pathways ◽  
Outer Mitochondrial Membrane ◽  
Endomembrane System ◽  
Inner Mitochondrial Membrane ◽  
Mitochondrial Inner Membrane ◽  
Functional Analyses ◽  
Made In

ABSTRACTOf the four separate PE biosynthetic pathways in eukaryotes, one occurs in the mitochondrial inner membrane (IM) and is executed by phosphatidylserine decarboxylase (Psd1p). Deletion of Psd1, which is lethal in mice, compromises mitochondrial function. We hypothesize that this reflects inefficient import of non-mitochondrial PE into the IM. To test this, we re-wired PE metabolism in yeast by re-directing Psd1p to the outer mitochondrial membrane or the endomembrane system. Our biochemical and functional analyses identified the IMS as the greatest barrier for PE import and demonstrated that PE synthesis in the IM is critical for cytochromebc1complex (III) function. Importantly, mutations predicted to disrupt a conserved PE-binding site in the complex III subunit, Qcr7p, impaired complex III activity similar toPSD1deletion. Collectively, these data demonstrate that PE made in the IM by Psd1p is critical to support the intrinsic functionality of complex III and establish one likely mechanism.

scholarly journals Tim50’s presequence receptor domain is essential for signal driven transport across the TIM23 complex

2011 ◽  
Vol 195 (4) ◽  
pp. 643-656 ◽  
Author(s):  
Christian Schulz ◽  
Oleksandr Lytovchenko ◽  
Jonathan Melin ◽  
Agnieszka Chacinska ◽  
Bernard Guiard ◽  
...  
Keyword(s):  
Binding Sites ◽  
Mitochondrial Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Mitochondrial Proteins ◽  
Outer Mitochondrial Membrane ◽  
Inner Mitochondrial Membrane ◽  
Mitochondrial Protein Import ◽  
Targeting Signals ◽  
Receptor Domain

N-terminal targeting signals (presequences) direct proteins across the TOM complex in the outer mitochondrial membrane and the TIM23 complex in the inner mitochondrial membrane. Presequences provide directionality to the transport process and regulate the transport machineries during translocation. However, surprisingly little is known about how presequence receptors interact with the signals and what role these interactions play during preprotein transport. Here, we identify signal-binding sites of presequence receptors through photo-affinity labeling. Using engineered presequence probes, photo cross-linking sites on mitochondrial proteins were mapped mass spectrometrically, thereby defining a presequence-binding domain of Tim50, a core subunit of the TIM23 complex that is essential for mitochondrial protein import. Our results establish Tim50 as the primary presequence receptor at the inner membrane and show that targeting signals and Tim50 regulate the Tim23 channel in an antagonistic manner.

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