scholarly journals The C-terminal domain of Fcj1 is required for formation of crista junctions and interacts with the TOB/SAM complex in mitochondria

2012 ◽  
Vol 23 (11) ◽  
pp. 2143-2155 ◽  
Author(s):  
Christian Körner ◽  
Miguel Barrera ◽  
Jovana Dukanovic ◽  
Katharina Eydt ◽  
Max Harner ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Inner Membrane ◽  
Functional Roles ◽  
Architectural Elements ◽  
Contact Sites ◽  
Oligomer Formation ◽  
Terminal Domain ◽  
Moderate Reduction ◽  
Close Proximity ◽  
Inner Membrane Protein

Crista junctions (CJs) are tubular invaginations of the inner membrane of mitochondria that connect the inner boundary with the cristae membrane. These architectural elements are critical for mitochondrial function. The yeast inner membrane protein Fcj1, called mitofilin in mammals, was reported to be preferentially located at CJs and crucial for their formation. Here we investigate the functional roles of individual domains of Fcj1. The most conserved part of Fcj1, the C-terminal domain, is essential for Fcj1 function. In its absence, formation of CJ is strongly impaired and irregular, and stacked cristae are present. This domain interacts with full-length Fcj1, suggesting a role in oligomer formation. It also interacts with Tob55 of the translocase of outer membrane β-barrel proteins (TOB)/sorting and assembly machinery (SAM) complex, which is required for the insertion of β-barrel proteins into the outer membrane. The association of the TOB/SAM complex with contact sites depends on the presence of Fcj1. The biogenesis of β-barrel proteins is not significantly affected in the absence of Fcj1. However, down-regulation of the TOB/SAM complex leads to altered cristae morphology and a moderate reduction in the number of CJs. We propose that the C-terminal domain of Fcj1 is critical for the interaction of Fcj1 with the TOB/SAM complex and thereby for stabilizing CJs in close proximity to the outer membrane. These results assign novel functions to both the C-terminal domain of Fcj1 and the TOB/SAM complex.

scholarly journals Repression of the Inner Membrane Lipoprotein NlpA by Rns in Enterotoxigenic Escherichia coli

2006 ◽  
Vol 189 (5) ◽  
pp. 1627-1632 ◽  
Author(s):  
Maria D. Bodero ◽  
M. Carolina Pilonieta ◽  
George P. Munson
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Enterotoxigenic Escherichia Coli ◽  
Start Codon ◽  
Inner Membrane ◽  
E Coli ◽  
Inner Membrane Protein

ABSTRACT The expression of the inner membrane protein NlpA is repressed by the enterotoxigenic Escherichia coli (ETEC) virulence regulator Rns, a member of the AraC/XylS family. The Rns homologs CfaD from ETEC and AggR from enteroaggregative E. coli also repress expression of nlpA. In vitro DNase I and potassium permanganate footprinting revealed that Rns binds to a site overlapping the start codon of nlpA, preventing RNA polymerase from forming an open complex at nlpAp. A second Rns binding site between positions −152 and −195 relative to the nlpA transcription start site is not required for repression. NlpA is not essential for growth of E. coli under laboratory conditions, but it does contribute to the biogenesis of outer membrane vesicles. As outer membrane vesicles have been shown to contain ETEC heat-labile toxin, the repression of nlpA may be an indirect mechanism through which the virulence regulators Rns and CfaD limit the release of toxin.

CHANGES IN THE MITOCHONDRIAL DOUBLE MEMBRANE IN TAPETAL AND SPOROGENIC CELLS IN CYTOPLASMIC MALE STERILE ANTHERS OF PETUNIA

1994 ◽  
Vol 42 (3) ◽  
pp. 173-181
Author(s):  
Dalia Evenor ◽  
Andrey Franck ◽  
Yona Tabib ◽  
Aaron Zelcer ◽  
Shamay Izhar ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mitochondrial Membrane ◽  
Early Prophase ◽  
Male Sterile ◽  
Inner Membrane ◽  
Double Membrane ◽  
Cytoplasmic Male Sterile ◽  
Ultrastructural Studies ◽  
Contact Sites ◽  
Close Proximity

Comparative histological and ultrastructural studies were made on the gametogenesis and microsporogenesis in isonuclear fertile and cytoplasmic male sterile petunia lines. Using electron microscopy, changes in the mitochondrial double membrane were observed in the tapetal and sporogenic cells of cytoplasmic male sterile anthers as the first cytological sign of breakdown of the process of microsporogenesis at early prophase I. These changes were manifested by a larger space between the outer and the inner membrane and fewer sites of close proximity (“contact sites”) in the sterile mitochondria, as compared to fertile mitochondria. The mitochondrial membrane of the parietal tissue in the cytoplasmic male sterile anthers was not affected in the same way. Even when total breakdown was already obvious in the tapetal and sporogenic cells, the mitochondria of the parietal layer remained intact.

scholarly journals Role of the intermembrane-space domain of the preprotein receptor Tom22 in protein import into mitochondria.

1996 ◽  
Vol 16 (8) ◽  
pp. 4035-4042 ◽  
Author(s):  
D A Court ◽  
F E Nargang ◽  
H Steiner ◽  
R S Hodges ◽  
W Neupert ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Protein Import ◽  
Protein Translocation ◽  
Specific Binding ◽  
Mitochondrial Outer Membrane ◽  
Intermembrane Space ◽  
Inner Membrane ◽  
Terminal Domain ◽  
Tom Complex

Tom22 is an essential component of the protein translocation complex (Tom complex) of the mitochondrial outer membrane. The N-terminal domain of Tom22 functions as a preprotein receptor in cooperation with Tom20. The role of the C-terminal domain of Tom22, which is exposed to the intermembrane space (IMS), in its own assembly into the Tom complex and in the import of other preproteins was investigated. The C-terminal domain of Tom22 is not essential for the targeting and assembly of this protein, as constructs lacking part or all of the IMS domain became imported into mitochondria and assembled into the Tom complex. Mutant strains of Neurospora expressing the truncated Tom22 proteins were generated by a novel procedure. These mutants displayed wild-type growth rates, in contrast to cells lacking Tom22, which are not viable. The import of proteins into the outer membrane and the IMS of isolated mutant mitochondria was not affected. Some but not all preproteins destined for the matrix and inner membrane were imported less efficiently. The reduced import was not due to impaired interaction of presequences with their specific binding site on the trans side of the outer membrane. Rather, the IMS domain of Tom22 appears to slightly enhance the efficiency of the transfer of these preproteins to the import machinery of the inner membrane.

scholarly journals Aim24 and MICOS modulate respiratory function, tafazzin-related cardiolipin modification and mitochondrial architecture

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Max Emanuel Harner ◽  
Ann-Katrin Unger ◽  
Toshiaki Izawa ◽  
Dirk M Walther ◽  
Cagakan Özbalci ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Respiratory Function ◽  
Structure And Function ◽  
Complete Loss ◽  
Mitochondrial Ultrastructure ◽  
Inner Membrane ◽  
Outer Membranes ◽  
Contact Sites ◽  
Inner Membrane Protein ◽  
And Function

Structure and function of mitochondria are intimately linked. In a search for components that participate in building the elaborate architecture of this complex organelle we have identified Aim24, an inner membrane protein. Aim24 interacts with the MICOS complex that is required for the formation of crista junctions and contact sites between inner and outer membranes. Aim24 is necessary for the integrity of the MICOS complex, for normal respiratory growth and mitochondrial ultrastructure. Modification of MICOS subunits Mic12 or Mic26 by His-tags in the absence of Aim24 leads to complete loss of cristae and respiratory complexes. In addition, the level of tafazzin, a cardiolipin transacylase, is drastically reduced and the composition of cardiolipin is modified like in mutants lacking tafazzin. In conclusion, Aim24 by interacting with the MICOS complex plays a key role in mitochondrial architecture, composition and function.

scholarly journals Crystallization and preliminary X-ray diffraction analysis of YejM from Salmonella typhimurium: an essential inner membrane protein involved in outer membrane directed cardiolipin transport

F1000Research ◽  
2017 ◽  
Vol 5 ◽  
pp. 1086
Author(s):  
Uma Gabale ◽  
Gene Qian ◽  
Elaina Roach ◽  
Susanne Ressl
Keyword(s):  
Membrane Protein ◽  
Diffraction Analysis ◽  
Outer Membrane ◽  
Drug Targets ◽  
Essential Gene ◽  
The United States ◽  
X Ray Diffraction ◽  
Inner Membrane ◽  
X Ray ◽  
Inner Membrane Protein

Salmonella  typhimurium is responsible for over 35% of all foodborne illness related hospitalizations in the United States. This Gram-negative bacterium possesses an inner and an outer membrane (OM), the latter allowing its survival and replication within host tissues. During infection, OM is remodeled by transport of glycerophospholipids across the periplasm and into the OM. Increased levels of cardiolipin in the OM were observed upon PhoPQ activation and led to the discovery of YejM; an inner membrane protein essential for cell growth involved in cardiolipin binding and transport to the OM. Here we report how YejM was engineered to facilitate crystal growth and X-ray diffraction analysis. Successful structure determination of YejM will help us understand how they interact and how YejM facilitates cardiolipin transport to the OM. Ultimately, yejm, being an essential gene, may lead to new drug targets inhibiting the pathogenic properties of S. typhimurium.

scholarly journals The essential inner membrane protein YejM is a metalloenzyme

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Uma Gabale ◽  
Perla Arianna Peña Palomino ◽  
HyunAh Kim ◽  
Wenya Chen ◽  
Susanne Ressl
Keyword(s):  
Antibiotic Resistance ◽  
Membrane Protein ◽  
Outer Membrane ◽  
Critical Role ◽  
Membrane Properties ◽  
Gram Negative Bacteria ◽  
Inner Membrane ◽  
Gram Negative ◽  
Periplasmic Domain ◽  
Inner Membrane Protein

Abstract Recent recurrent outbreaks of Gram-negative bacteria show the critical need to target essential bacterial mechanisms to fight the increase of antibiotic resistance. Pathogenic Gram-negative bacteria have developed several strategies to protect themselves against the host immune response and antibiotics. One such strategy is to remodel the outer membrane where several genes are involved. yejM was discovered as an essential gene in E. coli and S. typhimurium that plays a critical role in their virulence by changing the outer membrane permeability. How the inner membrane protein YejM with its periplasmic domain changes membrane properties remains unknown. Despite overwhelming structural similarity between the periplasmic domains of two YejM homologues with hydrolases like arylsulfatases, no enzymatic activity has been previously reported for YejM. Our studies reveal an intact active site with bound metal ions in the structure of YejM periplasmic domain. Furthermore, we show that YejM has a phosphatase activity that is dependent on the presence of magnesium ions and is linked to its function of regulating outer membrane properties. Understanding the molecular mechanism by which YejM is involved in outer membrane remodeling will help to identify a new drug target in the fight against the increased antibiotic resistance.

Microcins in action: amazing defence strategies of Enterobacteria

2012 ◽  
Vol 40 (6) ◽  
pp. 1456-1462 ◽  
Author(s):  
Sylvie Rebuffat
Keyword(s):  
Outer Membrane ◽  
Iron Acquisition ◽  
Gene Clusters ◽  
Inner Membrane ◽  
Post Translational Modifications ◽  
Bacterial Transcription ◽  
Outer Membrane Porin ◽  
Inner Membrane Protein ◽  
Living Organisms ◽  
Defence Strategies

Probably the oldest and most widespread antimicrobial strategy in living organisms is the use of antimicrobial peptides. Bacteria secrete such defence peptides, termed bacteriocins, that they use for microbial competitions. Microcins are bacteriocins of less than 10 kDa produced by Escherichia coli and related enterobacteria through the ribosomal pathway. They are synthesized as linear precursors, which can further undergo complex post-translational modifications resulting from dedicated maturation enzymes encoded in the microcin gene clusters, and are processed by proteolytic cleavage. Microcins exert potent bactericidal activities that use subtle and clever mechanisms to cross outer and inner membranes of Gram-negative bacteria. To cross the outer membrane, siderophore-microcins hijack receptors involved in iron acquisition. The lasso-peptide microcin J25, which is characterized by a knotted arrangement where the C-terminal tail is threaded through an N-terminal macrolactam ring, uses a hydroxamate siderophore receptor and the inner-membrane protein SbmA for import in sensitive bacteria, where it inhibits bacterial transcription through binding to RNAP (RNA polymerase). Microcin C produced as a heptapeptide adenylate, requires an outer-membrane porin and an inner-membrane ABC (ATP-binding-cassette) transporter to reach the cytoplasm of target bacteria, where it is processed by proteases into a non-hydrolysable aspartyl-adenylate analogue. Therefore, despite showing different killing mechanisms and the absence of any structural homology, microcins have the common characteristic to use Trojan horse strategies to destroy their competitors. They offer new and promising tracks for further design and engineering of novel efficient antibiotics.

Channel-forming colicins: translocation (and other deviant behaviour) associated with colicin Ia channel gating

1999 ◽  
Vol 32 (2) ◽  
pp. 189-205 ◽  
Author(s):  
Karen S. Jakes ◽  
Paul K. Kienker ◽  
Alan Finkelstein
Keyword(s):  
Outer Membrane ◽  
Target Cell ◽  
Single Channel ◽  
Protein Translocation ◽  
Inner Membrane ◽  
Toxic Activity ◽  
E Coli ◽  
Terminal Domain ◽  
Voltage Dependent ◽  
Colicin Ia

1. Introduction 1892. Channel properties 1912.1 Voltage-dependent gating 1912.2 Ion permeability 1932.2.1 Selectivity between potassium and chloride 1932.2.2 Permeability to large cations and large anions 1932.3 Single-channel characteristics 1942.4 Molecularity of the channel 1953. Colicin Ia channel topology and protein translocation 1953.1 Channels formed by whole colicin Ia 1953.1.1 General channel topology 1963.1.2 The translocated region 1993.1.3 The nonuniqueness of the upstream membrane-inserted segment 1993.2 Channels formed by the C-terminal domain of colicin Ia 2004. Concluding remarks 2025. Acknowledgement 2036. References 203Colicins are plasmid-encoded proteins, produced by some strains of E. coli, that kill other strains lacking the specific immunity protein encoded by the same plasmid. Most of the colicins have a three-domain structure: a central domain that binds to a receptor in the outer membrane of the target cell; an N-terminal domain that interacts with target cell proteins to move the C-terminal domain across the outer membrane and periplasmic space to the inner membrane; and a C-terminal domain that carries the toxic activity. In some colicins the C-terminal domain is an enzyme that kills the cell by entering the cytoplasm and attacking its DNA (e.g. colicin E2), its ribosomal RNA (e.g. colicin E3), or another target (Schaller et al. 1982; Ogawa et al. 1999). In other colicins, the C-terminal domain forms an ion-conducting channel in the inner membrane that ultimately leads to cell death by allowing essential solutes to leak out of the cell. These colicins, or their isolated C-terminal domains, can also form voltage-dependent channels in planar phospholipid bilayers. (For a review of the E colicins, including enzymatic colicins, see James et al. 1996; for a review of channel-forming colicins, see Cramer et al. 1995; and for a review of colicin import into E. coli, see Lazdunski et al. 1998.) The channel-forming colicins are the subject of this review, with particular emphasis on one member of this group, colicin Ia, and the protein translocation associated with the gating of its channel.

scholarly journals Sam50-Mic19-Mic60 axis Determines Mitochondrial Cristae Architecture by Mediating Mitochondrial Outer and Inner Membrane Contact

2018 ◽  
Author(s):  
Junhui Tang ◽  
Kuan Zhang ◽  
Jun Dong ◽  
Chaojun Yan ◽  
Shi Chen ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Intermembrane Space ◽  
Inner Membrane ◽  
Atp Production ◽  
Mitochondrial Intermembrane Space ◽  
Membrane Contact ◽  
Inner Membrane Protein

ABSTRACTMitochondrial cristae are critical for efficient oxidative phosphorylation, however, how cristae architecture is precisely organized remains largely unknown. Here, we discovered that Mic19, a core component of MICOS (mitochondrial contact site and cristae organizing system) complex, can be cleaved at N-terminal by mitochondrial protease OMA1. Mic19 directly interacts with mitochondrial outer-membrane protein Sam50 (the key subunit of SAM complex) and inner-membrane protein Mic60 (the key component of MICOS complex) to form Sam50-Mic19-Mic60 axis, which dominantly connects SAM and MICOS complexes to assemble MIB (mitochondrial intermembrane space bridging) supercomplex for mediating mitochondrial outer- and inner-membrane contact. OMA1-mediated Mic19 cleavage causes Sam50-Mic19-Mic60 axis disruption, which separates SAM and MICOS and leads to MIB disassembly. Disrupted Sam50-Mic19-Mic60 axis, even in the presence of SAM and MICOS complexes, causes the abnormal mitochondrial morphology, loss of mitochondrial cristae junctions, abnormal cristae distribution and reduced ATP production. Importantly, Sam50 displays punctate distribution at mitochondrial outer membrane, and acts as an anchoring point to guide the formation of mitochondrial cristae junctions. Therefore, we propose a model that Sam50-Mic19-Mic60 axis mediated SAM-MICOS complexes integration determines mitochondrial cristae architecture.

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