scholarly journals Modeling adsorption, conformation, and orientation of the Fis1 tail anchor at the mitochondrial outer membrane

2021 ◽  
Author(s):  
Beytullah Ozgur ◽  
Cory D. Dunn ◽  
Mehmet Sayar
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Outer Membrane ◽  
Coarse Grained ◽  
Carboxyl Terminus ◽  
Mitochondrial Outer Membrane ◽  
Substantial Evidence ◽  
Cytosolic Domain ◽  
Hydrophobic Amino Acids ◽  
Coarse Grained Simulations

Proteins can be targeted to organellar membranes using a tail anchor (TA), a stretch of hydrophobic amino acids found at the polypeptide carboxyl-terminus. The Fis1 protein (Fis1p), which promotes mitochondrial and peroxisomal division in the yeast Saccharomyces cerevisiae, is targeted to those organelles by its TA. Substantial evidence suggests that Fis1p insertion into the mitochondrial outer membrane can occur without the need for a translocation machinery. However, recent findings raise the possibility that Fis1p insertion into mitochondria might be promoted by a proteinaceous complex. Here, we have performed atomistic and coarse-grained simulations to analyze the adsorption, conformation and orientation of the Fis1(TA). Our results support stable insertion at the mitochondrial outer membrane in a monotopic, rather than a bitopic (transmembrane), configuration. Once inserted in the monotopic orientation, unassisted transition to the bitopic orientation is expected to be blocked by the highly charged nature of the TA carboxyl-terminus and by the Fis1p cytosolic domain. Our results are consistent with a model in which Fis1p does not require a translocation machinery for insertion at mitochondria.

An Artificial Mitochondrial Tail Signal/Anchor Sequence Confirms a Requirement for Moderate Hydrophobicity for Targeting

2007 ◽  
Vol 27 (6) ◽  
pp. 385-401 ◽  
Author(s):  
Binks W. Wattenberg ◽  
Denise Clark ◽  
Stephanie Brock
Keyword(s):  
Amino Acids ◽  
Endoplasmic Reticulum ◽  
Outer Membrane ◽  
Helical Structure ◽  
Mitochondrial Outer Membrane ◽  
Carboxy Terminus ◽  
Charged Amino Acids ◽  
Hydrophobic Amino Acids ◽  
Signal Anchor ◽  
Anchor Sequence

Tail-anchored proteins are a group of membrane proteins oriented with their amino terminus in the cytoplasm and their carboxy terminus embedded in intracellular membranes. This group includes the apoptosis-mediating proteins of the Bcl-2 family as well as the vesicle targeting proteins of the SNARE group, among others. A stretch of hydrophobic amino acids at the extreme carboxy terminus of these proteins serves both as a membrane anchor and as a targeting signal. Tail-anchored proteins are differentially targeted to either the endoplasmic reticulum or the mitochondrial outer membrane and the mechanism which accomplishes this selective targeting is poorly understood. Here we define important characteristics of the signal/anchor region which directs proteins to the mitochondrial outer membrane. We have created an artificial sequence consisting of a stretch of 16 leucines bounded by positively charged amino acids. Using this template we demonstrate that moderate hydrophobicity distinguishes the mitochondrial tail-anchor sequence from that of the endoplasmic reticulum tail-anchor sequence. A change as small as introduction of a single polar residue into a sequence that otherwise targets to the endoplasmic reticulum can substantially switch targeting to the mitochondrial outer membrane. Further we show that a mitochondrially targeted tail-anchor has a higher propensity for the formation of alpha-helical structure than a sequence directing tail-anchored proteins to the endoplasmic reticulum.

Integral membrane proteins in the mitochondrial outer membrane of Saccharomyces cerevisiae

FEBS Journal ◽  
2006 ◽  
Vol 273 (7) ◽  
pp. 1507-1515 ◽  
Author(s):  
Lena Burri ◽  
Katherine Vascotto ◽  
Ian E. Gentle ◽  
Nickie C. Chan ◽  
Traude Beilharz ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Integral Membrane Proteins ◽  
Mitochondrial Outer Membrane

scholarly journals Prohibitin Family Members Interact Genetically with Mitochondrial Inheritance Components in Saccharomyces cerevisiae

1998 ◽  
Vol 18 (7) ◽  
pp. 4043-4052 ◽  
Author(s):  
Karen H. Berger ◽  
Michael P. Yaffe
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Outer Membrane ◽  
Integral Membrane Proteins ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Mitochondrial Inheritance ◽  
Loss Of Function ◽  
Wild Type ◽  
Mitochondrial Inner Membrane ◽  
Synthetically Lethal

ABSTRACT Phb2p, a homolog of the tumor suppressor protein prohibitin, was identified in a genetic screen for suppressors of the loss of Mdm12p, a mitochondrial outer membrane protein required for normal mitochondrial morphology and inheritance in Saccharomyces cerevisiae. Phb2p and its homolog, prohibitin (Phb1p), were localized to the mitochondrial inner membrane and characterized as integral membrane proteins which depend on each other for their stability. In otherwise wild-type genetic backgrounds, null mutations in PHB1 andPHB2 did not confer any obvious phenotypes. However, loss of function of either PHB1 or PHB2 in cells with mitochondrial DNA deleted led to altered mitochondrial morphology, and phb1 or phb2 mutations were synthetically lethal when combined with a mutation in any of three mitochondrial inheritance components of the mitochondrial outer membrane, Mdm12p, Mdm10p, and Mmm1p. These results provide the first evidence of a role for prohibitin in mitochondrial inheritance and in the regulation of mitochondrial morphology.

scholarly journals OM14 is a mitochondrial receptor for cytosolic ribosomes that supports co-translational import into mitochondria

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Chen Lesnik ◽  
Yifat Cohen ◽  
Avigail Atir-Lande ◽  
Maya Schuldiner ◽  
Yoav Arava
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Strong Support ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Import ◽  
Translational Mode ◽  
Nascent Chain ◽  
Cytosolic Ribosomes

Abstract It is well established that import of proteins into mitochondria can occur after their complete synthesis by cytosolic ribosomes. Recently, an additional model was revived, proposing that some proteins are imported co-translationally. This model entails association of ribosomes with the mitochondrial outer membrane, shown to be mediated through the ribosome-associated chaperone nascent chain-associated complex (NAC). However, the mitochondrial receptor of this complex is unknown. Here, we identify the Saccharomyces cerevisiae outer membrane protein OM14 as a receptor for NAC. OM14Δ mitochondria have significantly lower amounts of associated NAC and ribosomes, and ribosomes from NAC[Δ] cells have reduced levels of associated OM14. Importantly, mitochondrial import assays reveal a significant decrease in import efficiency into OM14Δ mitochondria, and OM14-dependent import necessitates NAC. Our results identify OM14 as the first mitochondrial receptor for ribosome-associated NAC and reveal its importance for import. These results provide a strong support for an additional, co-translational mode of import into mitochondria.

scholarly journals Role of the Negative Charges in the Cytosolic Domain of TOM22 in the Import of Precursor Proteins into Mitochondria

1998 ◽  
Vol 18 (6) ◽  
pp. 3173-3181 ◽  
Author(s):  
Frank E. Nargang ◽  
Doron Rapaport ◽  
R. Gary Ritzel ◽  
Walter Neupert ◽  
Roland Lill
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Outer Membrane ◽  
Wild Type ◽  
Binding Studies ◽  
Amino Terminal ◽  
Precursor Proteins ◽  
Mutant Strains ◽  
Cytosolic Domain ◽  
Charged Residues ◽  
Positively Charged

ABSTRACT TOM22 is an essential mitochondrial outer membrane protein required for the import of precursor proteins into the organelles. The amino-terminal 84 amino acids of TOM22 extend into the cytosol and include 19 negatively and 6 positively charged residues. This region of the protein is thought to interact with positively charged presequences on mitochondrial preproteins, presumably via electrostatic interactions. We constructed a series of mutant derivatives of TOM22 in which 2 to 15 of the negatively charged residues in the cytosolic domain were changed to their corresponding amido forms. The mutant constructs were transformed into a sheltered Neurospora crassa heterokaryon bearing atom22::hygromycin R disruption in one nucleus. All constructs restored viability to the disruption-carrying nucleus and gave rise to homokaryotic strains containing mutanttom22 alleles. Isolated mitochondria from three representative mutant strains, including the mutant carrying 15 neutralized residues (strain 861), imported precursor proteins at efficiencies comparable to those for wild-type organelles. Precursor binding studies with mitochondrial outer membrane vesicles from several of the mutant strains, including strain 861, revealed only slight differences from binding to wild-type vesicles. Deletion mutants lacking portions of the negatively charged region of TOM22 can also restore viability to the disruption-containing nucleus, but mutants lacking the entire region cannot. Taken together, these data suggest that an abundance of negative charges in the cytosolic domain of TOM22 is not essential for the binding or import of mitochondrial precursor proteins; however, other features in the domain are required.

scholarly journals Dynamics of the TOM Complex of Mitochondria during Binding and Translocation of Preproteins

1998 ◽  
Vol 18 (9) ◽  
pp. 5256-5262 ◽  
Author(s):  
Doron Rapaport ◽  
Klaus-Peter Künkele ◽  
Markus Dembowski ◽  
Uwe Ahting ◽  
Frank E. Nargang ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Outer Membrane ◽  
Mitochondrial Outer Membrane ◽  
Initial Contact ◽  
Amino Acid Residues ◽  
Mitochondrial Targeting ◽  
Critical Feature ◽  
Structural Alterations ◽  
Tom Complex ◽  
Oligomeric Assembly

ABSTRACT Translocation of preproteins across the mitochondrial outer membrane is mediated by the TOM complex. This complex consists of receptor components for the initial contact with preproteins at the mitochondrial surface and membrane-embedded proteins which promote transport and form the translocation pore. In order to understand the interplay between the translocating preprotein and the constituents of the TOM complex, we analyzed the dynamics of the TOM complex ofNeurospora crassa and Saccharomyces cerevisiaemitochondria by following the structural alterations of the essential pore component Tom40 during the translocation of preproteins. Tom40 exists in a homo-oligomeric assembly and dynamically interacts with Tom6. The Tom40 assembly is influenced by a block of negatively charged amino acid residues in the cytosolic domain of Tom22, indicating a cross-talk between preprotein receptors and the translocation pore. Preprotein binding to specific sites on either side of the outer membrane (cis and trans sites) induces distinct structural alterations of Tom40. To a large extent, these changes are mediated by interaction with the mitochondrial targeting sequence. We propose that such targeting sequence-induced adaptations are a critical feature of translocases in order to facilitate the movement of preproteins across cellular membranes.

scholarly journals The Mitochondrial TOM Complex Is Required for tBid/Bax-induced Cytochrome c Release

2007 ◽  
Vol 282 (38) ◽  
pp. 27633-27639 ◽  
Author(s):  
Martin Ott ◽  
Erik Norberg ◽  
Katharina M. Walter ◽  
Patrick Schreiner ◽  
Christian Kemper ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Outer Membrane ◽  
Recombinant Proteins ◽  
Mitochondrial Membrane ◽  
Mitochondrial Outer Membrane ◽  
Intermembrane Space ◽  
Outer Mitochondrial Membrane ◽  
Cytochrome C Release ◽  
Unknown Mechanism

Cytochrome c release from mitochondria is a key event in apoptosis signaling that is regulated by Bcl-2 family proteins. Cleavage of the BH3-only protein Bid by multiple proteases leads to the formation of truncated Bid (tBid), which, in turn, promotes the oligomerization/insertion of Bax into the mitochondrial outer membrane and the resultant release of proteins residing in the intermembrane space. Bax, a monomeric protein in the cytosol, is targeted by a yet unknown mechanism to the mitochondria. Several hypotheses have been put forward to explain this targeting specificity. Using mitochondria isolated from different mutants of the yeast Saccharomyces cerevisiae and recombinant proteins, we have now investigated components of the mitochondrial outer membrane that might be required for tBid/Bax-induced cytochrome c release. Here, we show that the protein translocase of the outer mitochondrial membrane is required for Bax insertion and cytochrome c release.

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