Structure of crystalline VDAC, the voltage-gated channel in the mitochondrial outer membrane

1992 ◽  
Vol 50 (1) ◽  
pp. 440-441
Author(s):  
X.W. Guo ◽  
P.R. Smith ◽  
M. Radermacher ◽  
C.A. Mannella
Keyword(s):  
Neurospora Crassa ◽  
Outer Membrane ◽  
Repeat Unit ◽  
Mitochondrial Outer Membrane ◽  
Lattice Contraction ◽  
Outer Membranes ◽  
Voltage Gated ◽  
Lateral Contraction ◽  
Gated Channel ◽  
Projection Images

The voltage-gated, mitochondrial channel, VDAC, is formed by a 31-kDa outer-membrane polypeptide. Crystalline arrays of this channel, produced by phospholipase A2 treatment of Neurospora crassa mitochondrial outer membranes, consist of groups of 6 channels repeated on a parallelogram (“oblique”) lattice (a=13.3nm, b=11.5nm, γ = 109°). These membrane crystals are polymorphic, i.e. lateral contraction is triggered by a polyanion which also decreases VDAC’s gating potential. Projection images of unstained, frozen-hydrated VDAC arrays indicate that lattice contraction is accompanied by changes in the distribution of protein away from the hexameric repeat unit.

scholarly journals Mitochondrial Outer Membrane Proteins Assist Bid in Bax-mediated Lipidic Pore Formation

2009 ◽  
Vol 20 (8) ◽  
pp. 2276-2285 ◽  
Author(s):  
Blanca Schafer ◽  
Joel Quispe ◽  
Vineet Choudhary ◽  
Jerry E. Chipuk ◽  
Teddy G. Ajero ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Pore Formation ◽  
Outer Membrane Proteins ◽  
Mitochondrial Outer Membrane ◽  
Outer Membranes ◽  
Mitochondrial Outer Membrane Permeabilization ◽  
In Vitro Systems ◽  
Large Round ◽  
Key Features

Mitochondrial outer membrane permeabilization (MOMP) is a critical step in apoptosis and is regulated by Bcl-2 family proteins. In vitro systems using cardiolipin-containing liposomes have demonstrated the key features of MOMP induced by Bax and cleaved Bid; however, the nature of the “pores” and how they are formed remain obscure. We found that mitochondrial outer membranes contained very little cardiolipin, far less than that required for liposome permeabilization, despite their responsiveness to Bcl-2 family proteins. Strikingly, the incorporation of isolated mitochondrial outer membrane (MOM) proteins into liposomes lacking cardiolipin conferred responsiveness to cleaved Bid and Bax. Cardiolipin dependence was observed only when permeabilization was induced with cleaved Bid but not with Bid or Bim BH3 peptide or oligomerized Bax. Therefore, we conclude that MOM proteins specifically assist cleaved Bid in Bax-mediated permeabilization. Cryoelectron microscopy of cardiolipin-liposomes revealed that cleaved Bid and Bax produced large round holes with diameters of 25–100 nm, suggestive of lipidic pores. In sum, we propose that activated Bax induces lipidic pore formation and that MOM proteins assist cleaved Bid in this process in the absence of cardiolipin.

Nature of In-Plane Phase Transitions in 2D Crystals of the Mitochondrial Porin, VDAC

1997 ◽  
Vol 3 (S2) ◽  
pp. 1065-1066
Author(s):  
C.A. Mannella
Keyword(s):  
Electron Microscopy ◽  
Phase Transitions ◽  
Pore Structure ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Porin ◽  
Outer Membranes ◽  
Voltage Gated ◽  
Bacterial Porins ◽  
Source Of Information ◽  
2D Crystals

VDAC is a voltage-gated ion and metabolite channel that occurs at high density in the mitochondrial outer membrane. Although VDAC is probably related structurally to bacterial porins, small transmembrane voltages cause it to undergo reversible, partial closures that are not seen with the prokaryotic pores. The “closed” states, which are impermeable to ATP, can be induced by effectors, including a synthetic polyanion. There is evidence that closure involves major rearrangements of the pore structure that are difficult to explain in terms of porin-like β-barrels.The main source of information about the structure of VDAC is electron microscopy of 2D crystals obtained by phospholipase treatment of outer membranes of fungal mitochondria. The unit cell observed after partial lipid hydrolysis (a = 13.3 nm, b = 11.5 nm, γ = 109°) contains six pores which appear to be structurally equivalent at the resolution of correlation averages of crystals embedded in aurothioglucose or vitreous ice (∼1/1.5 nm−1).

scholarly journals A C-Terminally Truncated Variant of Neurospora crassa VDAC Assembles Into a Partially Functional Form in the Mitochondrial Outer Membrane and Forms Multimers in vitro

2021 ◽  
Vol 12 ◽  
Author(s):  
Fraser G. Ferens ◽  
William A. T. Summers ◽  
Ameet Bharaj ◽  
Jörg Stetefeld ◽  
Deborah A. Court
Keyword(s):  
Neurospora Crassa ◽  
Outer Membrane ◽  
Analytical Ultracentrifugation ◽  
Size Exclusion ◽  
Mitochondrial Outer Membrane ◽  
Voltage Dependent ◽  
Exclusion Chromatography ◽  
Selective Channel

The voltage-dependent anion-selective channel (VDAC) is a porin in the mitochondrial outer membrane (MOM). Unlike bacterial porins, several mitochondrial β-barrels comprise an odd number of β-strands, as is the case for the 19-β-stranded VDAC. Previously, a variant of a VDAC from Neurospora crassa, VDAC-ΔC, lacking the predicted 19th β-strand, was found to form gated, anion-selective channels in artificial membranes. In vivo, the two C-terminal β-strands (β18 and β19) in VDAC form a β-hairpin necessary for import from the cytoplasm into mitochondria and the β-signal required for assembly in the mitochondrial outer membrane resides in β19. The current study demonstrated that the putative 18-stranded β-barrel formed by VDAC-ΔC can be imported and assembled in the MOM in vivo and can also partially rescue the phenotype associated with the deletion of VDAC from a strain of N. crassa. Furthermore, when expressed and purified from Escherichia coli, VDAC-ΔC can be folded into a β-strand-rich form in decyl-maltoside. Size exclusion chromatography (SEC) alone or combined with multi-angle light scattering (SEC-MALS) and analytical ultracentrifugation revealed that, unlike full-length VDACs, VDAC-ΔC can self-organize into dimers and higher order oligomers in the absence of sterol.

Identification of the mutated sites present in the transmembrane regions of SCN1A_HUMAN (Sodium Voltage-Gated Channel Alpha Subunit 1) using Insilico techniques

2020 ◽  
Vol 5 (1) ◽  
pp. 1-6
Author(s):  
Balaji Munivelan
Keyword(s):  
Amino Acids ◽  
Outer Membrane ◽  
Structure Prediction ◽  
Homology Modelling ◽  
Transmembrane Helix ◽  
3D Structure ◽  
Docking Studies ◽  
Alpha Subunit ◽  
Voltage Gated ◽  
Gated Channel

Mutations in numerous genes which encode for voltage-gated sodium channels give rise to various epilepsy syndromes in humans. Our research investigation mainly focuses on the identification of the integral membrane protein of the SCN1A (Sodium Voltage-Gated Channel Alpha Subunit 1) in humans. Secondary, we focus on the transmembrane membrane (TP) amino acids directly involved in the epilepsy-involved mutated regions. Using Insilico protocols, we identify the TP proteins and amino acids and elucidate the Transmembrane Helix and the inside and outside amino acids regions of the SCN1A. With the help of Insilico proteomics server, the amino acids in the mutated regions involved in the TP were identified. Finally, 3D structure prediction was performed using homology modelling server and the modelled structure was cross validated for the TP and validated. The identified results were validated using molecular visualization tools. We prove that the mutated amino acids are present in the outer membrane of the TP regions. Thus, the outer membrane of sodium channel and the amino acids present in the outer membrane (T875M, R859C, and R1648H) play a vital role in Structure-Based Drug Designing and Drug Docking studies.

Characterization of rat TOM70 as a receptor of the preprotein translocase of the mitochondrial outer membrane

2002 ◽  
Vol 115 (9) ◽  
pp. 1895-1905 ◽  
Author(s):  
Hiroyuki Suzuki ◽  
Maki Maeda ◽  
Katsuyoshi Mihara
Keyword(s):  
Outer Membrane ◽  
Transmembrane Domain ◽  
Structural Similarity ◽  
Mitochondrial Outer Membrane ◽  
Outer Membranes ◽  
Sequence Identity ◽  
Arginine Residues ◽  
Targeting Signal ◽  
Mitochondria Targeting

We cloned a ∼70 kDa rat mitochondrial outer membrane protein (OM70)with a sequence identity of 28.1% and 20.1% with N. crassa and S. cerevisiae Tom70, respectively. Even with this low sequence identity,however, the proteins share a remarkable structural similarity: they have 7-10 tetratricopeptide repeat motifs and are anchored to the outer membrane through the N-terminal transmembrane domain with the bulk portion located in the cytosol. Antibodies against OM70 inhibited import of preproteins, such as the ADP/ATP carrier and rTOM40, that use internal targeting signals but not the import of cleavable presequence-containing preproteins. Blue native gel electrophoresis and immunoprecipitation of digitoninsolubilized mitochondrial outer membranes revealed that OM70 was loosely associated with the ∼400 kDa translocase complex of the mitochondrial outer membrane, which contains rTOM22 and rTOM40. A yeast two-hybrid system demonstrated that OM70 interacted with rTOM20 and rTOM22 through the cytoplasmic domains. Thus, OM70 is a functional homologue of fungal Tom70 and functions as a receptor of the preprotein import machinery of the rat mitochondrial outer membrane. Furthermore, the N-terminal 66 residue region of OM70, which comprises a hydrophilic 41 residue N-terminal domain, a 22 residue transmembrane domain and three arginine residues, is sufficient to act as a mitochondria-targeting signal, and the arginine cluster is crucial for this function.

scholarly journals Roles of the Mdm10, Tom7, Mdm12, and Mmm1 Proteins in the Assembly of Mitochondrial Outer Membrane Proteins in Neurospora crassa

2010 ◽  
Vol 21 (10) ◽  
pp. 1725-1736 ◽  
Author(s):  
Jeremy G. Wideman ◽  
Nancy E. Go ◽  
Astrid Klein ◽  
Erin Redmond ◽  
Sebastian W.K. Lackey ◽  
...  
Keyword(s):  
Neurospora Crassa ◽  
Outer Membrane ◽  
Double Mutant ◽  
Outer Membrane Proteins ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Functions ◽  
Mitochondrial Distribution ◽  
Additive Loss ◽  
The Individual ◽  
Relationship Of

The Mdm10, Mdm12, and Mmm1 proteins have been implicated in several mitochondrial functions including mitochondrial distribution and morphology, assembly of β-barrel proteins such as Tom40 and porin, association of mitochondria and endoplasmic reticulum, and maintaining lipid composition of mitochondrial membranes. Here we show that loss of any of these three proteins in Neurospora crassa results in the formation of large mitochondrial tubules and reduces the assembly of porin and Tom40 into the outer membrane. We have also investigated the relationship of Mdm10 and Tom7 in the biogenesis of β-barrel proteins. Previous work showed that mitochondria lacking Tom7 assemble Tom40 more efficiently, and porin less efficiently, than wild-type mitochondria. Analysis of mdm10 and tom7 single and double mutants, has demonstrated that the effects of the two mutations are additive. Loss of Tom7 partially compensates for the decrease in Tom40 assembly resulting from loss of Mdm10, whereas porin assembly is more severely reduced in the double mutant than in either single mutant. The additive effects observed in the double mutant suggest that different steps in β-barrel assembly are affected in the individual mutants. Many aspects of Tom7 and Mdm10 function in N. crassa are different from those of their homologues in Saccharomyces cerevisiae.

scholarly journals Mitochondria can recognize and assemble fragments of a β-barrel structure

2011 ◽  
Vol 22 (10) ◽  
pp. 1638-1647 ◽  
Author(s):  
Jonas E.N. Müller ◽  
Drazen Papic ◽  
Thomas Ulrich ◽  
Iwan Grin ◽  
Monika Schütz ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Structural Features ◽  
Yeast Cells ◽  
Mitochondrial Outer Membrane ◽  
Gram Negative Bacteria ◽  
Mitochondrial Targeting ◽  
Outer Membranes ◽  
Specific Targeting ◽  
Linear Sequence ◽  
Endosymbiotic Origin

β-barrel proteins are found in the outer membranes of eukaryotic organelles of endosymbiotic origin as well as in the outer membrane of Gram-negative bacteria. Precursors of mitochondrial β-barrel proteins are synthesized in the cytosol and have to be targeted to the organelle. Currently, the signal that assures their specific targeting to mitochondria is poorly defined. To characterize the structural features needed for specific mitochondrial targeting and to test whether a full β-barrel structure is required, we expressed in yeast cells the β-barrel domain of the trimeric autotransporter Yersinia adhesin A (YadA). Trimeric autotransporters are found only in prokaryotes, where they are anchored to the outer membrane by a single 12-stranded β-barrel structure to which each monomer is contributing four β-strands. Importantly, we found that YadA is solely localized to the mitochondrial outer membrane, where it exists in a native trimeric conformation. These findings demonstrate that, rather than a linear sequence or a complete β-barrel structure, four β-strands are sufficient for the mitochondria to recognize and assemble a β-barrel protein. Remarkably, the evolutionary origin of mitochondria from bacteria enables them to import and assemble even proteins belonging to a class that is absent in eukaryotes.

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