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Journal ArticleDOI

AAA proteases with catalytic sites on opposite membrane surfaces comprise a proteolytic system for the ATP-dependent degradation of inner membrane proteins in mitochondria.

15 Aug 1996-The EMBO Journal (John Wiley & Sons, Ltd)-Vol. 15, Iss: 16, pp 4218-4229
TL;DR: Two AAA proteases with their catalytic sites on opposite membrane surfaces constitute a novel proteolytic system for the degradation of membrane proteins in mitochondria.
Abstract: The mechanism of selective protein degradation of membrane proteins in mitochondria has been studied employing a model protein that is subject to rapid proteolysis within the inner membrane. Protein degradation was mediated by two different proteases: (i) the m-AAA protease, a protease complex consisting of multiple copies of the ATP-dependent metallopeptidases Yta1Op (Afg3p) and Yta12p (Rcalp); and (ii) by Ymelp (Ytallp) that also is embedded in the inner membrane. Ymelp, highly homologous to Yta1Op and Yta12p, forms a complex of approximately 850 kDa in the inner membrane and exerts ATP-dependent metallopeptidase activity. While the m-AAA protease exposes catalytic sites to the mitochondrial matrix, Ymelp is active in the intermembrane space. The Ymelp complex was therefore termed 'i-AAA protease'. Analysis of the proteolytic fragments indicated cleavage of the model polypeptide at the inner and outer membrane surface and within the membrane-spanning domain. Thus, two AAA proteases with their catalytic sites on opposite membrane surfaces constitute a novel proteolytic system for the degradation of membrane proteins in mitochondria.
Citations
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Journal ArticleDOI
TL;DR: This study definitively identifies the chloroplast protease acting on the D1 protein during its light-induced turnover, and represents a novel class of FtsH substrate— functionally assembled proteins that have undergone irreversible photooxidative damage and cleavage.
Abstract: The photosystem II reaction center D1 protein is known to turn over frequently. This protein is prone to irreversible damage caused by reactive oxygen species that are formed in the light; the damaged, nonfunctional D1 protein is degraded and replaced by a new copy. However, the proteases responsible for D1 protein degradation remain unknown. In this study, we investigate the possible role of the FtsH protease, an ATP-dependent zinc metalloprotease, during this process. The primary light-induced cleavage product of the D1 protein, a 23-kD fragment, was found to be degraded in isolated thylakoids in the dark during a process dependent on ATP hydrolysis and divalent metal ions, suggesting the involvement of FtsH. Purified FtsH degraded the 23-kD D1 fragment present in isolated photosystem II core complexes, as well as that in thylakoid membranes depleted of endogenous FtsH. In this study, we definitively identify the chloroplast protease acting on the D1 protein during its light-induced turnover. Unlike previously identified membrane-bound substrates for FtsH in bacteria and mitochondria, the 23-kD D1 fragment represents a novel class of FtsH substrate— functionally assembled proteins that have undergone irreversible photooxidative damage and cleavage.

370 citations


Cites background from "AAA proteases with catalytic sites ..."

  • ...Leonhard et al. (1996) suggested that the mitochondrial FtsH-like m-AAA protease participates in the partitioning of a membrane-bound model substrate to the catalytic site by virtue of its chaperone activity, thereby allowing cleavage between residues that normally are embedded in the lipid bilayer....

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Journal ArticleDOI
21 Oct 2005-Cell
TL;DR: A regulatory role of an AAA protease for mitochondrial protein synthesis in yeast is described and mitochondrial defects associated with m-AAA protease mutants in yeast are rationalize and shed new light on the mechanism of axonal degeneration in HSP.

361 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the current molecular understanding of mitophagy, and its physiological implications, and discuss how multiple mitophathy pathways coordinately modulate mitochondrial fitness and populations.
Abstract: Degradation of mitochondria via a selective form of autophagy, named mitophagy, is a fundamental mechanism conserved from yeast to humans that regulates mitochondrial quality and quantity control. Mitophagy is promoted via specific mitochondrial outer membrane receptors, or ubiquitin molecules conjugated to proteins on the mitochondrial surface leading to the formation of autophagosomes surrounding mitochondria. Mitophagy-mediated elimination of mitochondria plays an important role in many processes including early embryonic development, cell differentiation, inflammation, and apoptosis. Recent advances in analyzing mitophagy in vivo also reveal high rates of steady-state mitochondrial turnover in diverse cell types, highlighting the intracellular housekeeping role of mitophagy. Defects in mitophagy are associated with various pathological conditions such as neurodegeneration, heart failure, cancer, and aging, further underscoring the biological relevance. Here, we review our current molecular understanding of mitophagy, and its physiological implications, and discuss how multiple mitophagy pathways coordinately modulate mitochondrial fitness and populations.

352 citations

Journal ArticleDOI
TL;DR: It is demonstrated here that prohibitins regulate the turnover of membrane proteins by the m-AAA protease, a conserved ATP-dependent protease in the inner membrane of mitochondria, and functionally link members of two conserved protein families in eukaryotes to the degradation of membranes proteins in mitochondria.
Abstract: Prohibitins comprise a protein family in eukaryotic cells with potential roles in senescence and tumor suppression. Phb1p and Phb2p, members of the prohibitin family in Saccharomyces cerevisiae, have been implicated in the regulation of the replicative life span of the cells and in the maintenance of mitochondrial morphology. The functional activities of these proteins, however, have not been elucidated. We demonstrate here that prohibitins regulate the turnover of membrane proteins by the m-AAA protease, a conserved ATP-dependent protease in the inner membrane of mitochondria. The m-AAA protease is composed of the homologous subunits Yta10p (Afg3p) and Yta12p (Rca1p). Deletion of PHB1 or PHB2 impairs growth of Deltayta10 or Deltayta12 cells but does not affect cell growth in the presence of the m-AAA protease. A prohibitin complex with a native molecular mass of approximately 2 MDa containing Phb1p and Phb2p forms a supercomplex with the m-AAA protease. Proteolysis of nonassembled inner membrane proteins by the m-AAA protease is accelerated in mitochondria lacking Phb1p or Phb2p, indicating a negative regulatory effect of prohibitins on m-AAA protease activity. These results functionally link members of two conserved protein families in eukaryotes to the degradation of membrane proteins in mitochondria.

325 citations


Cites background from "AAA proteases with catalytic sites ..."

  • ...Thus, two large complexes which expose large domains to opposite membrane surfaces exist in the inner membrane and interact with each other: the Phb1p-Phb2p complex with an apparent molecular mass of approximately 2 MDa, and the m-AAA protease with an apparent molecular mass of approximately 1 MDa....

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  • ...They eluted in fractions corresponding to a native molecular mass of approximately 2 MDa under these conditions....

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  • ...Upon determination of the native molecular mass of the m-AAA protease by gel filtration, strikingly different results were obtained in the presence of different detergents: when mitochondrial membranes were extracted with digitonin, the m-AAA protease subunits Yta10p and Yta12p eluted from the column in a single peak which corresponded to a molecular mass greater than 2 MDa (Fig....

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  • ...Their catalytic sites, however, are exposed to opposite membrane surfaces: the m-AAA protease containing Yta10p (Afg3p) and Yta12p (Rca1p) acts on the matrix side, while the i-AAA protease containing Yme1p is active in the intermembrane space (3, 20)....

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  • ...In contrast, after solubilization of mitochondria with the nonionic detergent Triton X-100, both m-AAA protease subunits coeluted from the sizing column in fractions corresponding to a native molecular mass of approximately 1 MDa as reported previously (Fig....

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Journal ArticleDOI
TL;DR: The current understanding of UPR (mt) signal transduction and the impact of the UPR(mt) on diseased cells is reviewed.

310 citations

References
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Journal ArticleDOI
01 Jan 1986
TL;DR: The next generation of autonomous vehicles will be able to communicate with each other in a much more efficient and efficient manner than the current generation of vehicles that can communicate solely with the human eye.
Abstract: PERSPECTIVES AND OVERVIEW ............................................................................................................. 32

1,498 citations

Journal ArticleDOI
01 Jan 1990-Gene
TL;DR: A general and rapid method for site-directed mutagenesis using primed amplification by the polymerase chain reaction to construct mutants of the RNase T1-encoding gene using a double-stranded DNA template.

664 citations

Journal ArticleDOI
TL;DR: It is concluded that FtsH is a novel membrane‐bound, ATP‐dependent metalloprotease with activity for sigma 32, a key element in the regulation of the E. coli heat‐shock response.
Abstract: Escherichia coli FtsH is an essential integral membrane protein that has an AAA-type ATPase domain at its C-terminal cytoplasmic part, which is homologous to at least three ATPase subunits of the eukaryotic 26S proteasome. We report here that FtsH is involved in degradation of the heat-shock transcription factor sigma 32, a key element in the regulation of the E. coli heat-shock response. In the temperature-sensitive ftsH1 mutant, the amount of sigma 32 at a non-permissive temperature was higher than in the wild-type under certain conditions due to a reduced rate of degradation. In an in vitro system with purified components, FtsH catalyzed ATP-dependent degradation of biologically active histidine-tagged sigma 32. FtsH has a zinc-binding motif similar to the active site of zinc-metalloproteases. Protease activity of FtsH for histidine-tagged sigma 32 was stimulated by Zn2+ and strongly inhibited by the heavy metal chelating agent o-phenanthroline. We conclude that FtsH is a novel membrane-bound, ATP-dependent metalloprotease with activity for sigma 32. These findings indicate a new mechanism of gene regulation in E. coli.

437 citations

Journal ArticleDOI
TL;DR: This work proposes that the basic biochemical activity of the AAA module, a highly conserved module of 230 amino acids present in one or two copies in each protein, acts as an ATP‐dependent protein clamp.
Abstract: A fast growing family of ATPases has recently been highlighted. It was named the AAA family, for ATPases Associated to a variety of cellular Activities. The key feature of the family is a highly conserved module of 230 amino acids present in one or two copies in each protein. Despite extensive sequence conservation, the members of the family fulfil a large diversity of cellular functions: cell cycle regulation, gene expression in yeast and HIV, vesicle-mediated transport, peroxisome assembly, 26S protease function etc. In addition, several members of this family can be found in the same organism (up to 17 in S. cerevisiae). The contrast between functional diversity and structural conservation of the module, from archaebacteria to mammals, suggests that it plays an essential, but as yet unknown, role at key points of the cellular machinery. Two (non-exclusive) such possibilities are: (1) ATP-dependent proteasome function and (2) ATP-dependent anchorage of proteins. Finally, the basic biochemical activity of the AAA module is still a matter of speculation, and we propose that it acts as an ATP-dependent protein clamp.

342 citations

Journal ArticleDOI
TL;DR: The heat shock response in Escherichia coli is governed by the concentration of the highly unstable sigma factor sigma 32, and the essential protein HflB (FtsH), known to control proteolysis of the phage lambda cII protein, also governs sigma32 degradation.
Abstract: The heat shock response in Escherichia coli is governed by the concentration of the highly unstable sigma factor sigma 32. The essential protein HflB (FtsH), known to control proteolysis of the phage lambda cII protein, also governs sigma 32 degradation: an HflB-depleted strain accumulated sigma 32 and induced the heat shock response, and the half-life of sigma 32 increased by a factor up to 12 in mutants with reduced HflB function and decreased by a factor of 1.8 in a strain overexpressing HflB. The hflB gene is in the ftsJ-hflB operon, one promoter of which is positively regulated by heat shock and sigma 32. The lambda cIII protein, which stabilizes sigma 32 and lambda cII, appears to inhibit the HflB-governed protease. The E. coli HflB protein controls the stability of two master regulators, lambda cII and sigma 32, responsible for the lysis-lysogeny decision of phage lambda and the heat shock response of the host.

319 citations