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Query: EC:3.6.3.14 (ATP synthase)
 7,042 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A cDNA clone encoding the complete precursor of the delta subunit of chloroplast ATP synthase has been isolated from a tobacco (Nicotiana tabacum) leaf cDNA library in lambda gt11. The 880 bp insert encodes a polypeptide of 248 amino acid residues, of which 61 residues constitute an N-terminal presequence and 187 residues make up the mature delta subunit. Transcription and translation of the cDNA in vitro produced a protein of 29 kDa which was imported by isolated pea chloroplasts and processed to the mature 20 kDa subunit. The delta subunit precursor was processed to the mature size by a processing peptidase present in pea stromal extracts. Hybridisation of the cDNA to Southern blots of tobacco genomic DNA suggests the presence of two genes in the haploid genome.
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PMID:Import and processing of the precursor of the delta subunit of tobacco chloroplast ATP synthase. 142 Nov 56

A cDNA clone encoding the complete precursor of the gamma subunit of chloroplast ATP synthase has been isolated from a tobacco (Nicotiana tabacum) leaf cDNA library in lambda gt11. The 1.4 kb insert encodes a polypeptide of 377 amino acid residues, of which 55 residues constitute an N-terminal presequence and 322 residues make up the mature gamma subunit. Hybridisation of the cDNA to Southern blots of tobacco genomic DNA indicates the presence of two genes in the haploid genome. Transcription and translation of the cDNA in vitro produced a protein of 41 kDa which was imported by isolated pea chloroplasts and processed to the mature 36 kDa subunit. The gamma subunit precursor was processed to the mature size by a processing peptidase of 180 kDa present in pea stromal extracts.
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PMID:Import and processing of the precursor form of the gamma subunit of the chloroplast ATP synthase from tobacco. 153 3

In this study we report the first comparison of the mitochondrial protein import and processing events in two different tissues from the same organism. Both spinach leaf and root mitochondria were able to import and process the in vitro transcribed and translated Neurospora crassa F1 beta subunit of ATP synthase to the mature size product. Temperature optimum for protein import, 20 degrees C, was considerably lower than that found in other systems. In spinach leaf mitochondria, the processing peptidase has been shown to constitute an integral part of the bc1 complex of the respiratory chain. In accordance with these results, the majority of the processing activity in root mitochondria was also localized in the membrane. However, although the same amount of the processing peptidase was present per mg of membrane protein in both leaf and root mitochondria, as determined immunologically, the specific processing activity was several-fold higher in roots. Furthermore, in contrast to the processing enzyme in leaf, a portion of the processing activity could be disassociated from the root membrane with relatively weak salt treatment. The processing event in both the leaf and root membranes was always accompanied by a degradation of the F1 beta precursor. The degradation activity was found to be several-fold higher in roots than in leaves and was also partially dissociated from the membrane after salt treatment. Both the processing and degradation activities were inhibited by orthophenanthroline, a known metalloprotease inhibitor. These results show tissue-specific differences of the processing event catalyzed by the bc1 complex and indicate the presence of two populations of the processing peptidase in root mitochondria.
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PMID:Tissue-specific differences of the mitochondrial protein import machinery: in vitro import, processing and degradation of the pre-F1 beta subunit of the ATP synthase in spinach leaf and root mitochondria. 794 13

The CFoII subunit of the ATP synthase is an integral component of the thylakoid membrane which is synthesized in the cytosol with a bipartite, lumen-targeting presequence similar in structural terms to those of imported lumenal proteins such as plastocyanin. This presequence is shown to possess a terminal cleavage site for the thylakoidal processing peptidase, but no intermediate site for the stromal processing peptidase. The integration of CFoII into the thylakoid membrane of Pisum sativum has been analysed using in vitro assays for the import of proteins into intact chloroplasts or isolated thylakoids. Efficient integration into thylakoids is observed in the light and dark, and the integration process does not require the presence of either stromal extracts or nucleoside triphosphates. The uncoupler nigericin inhibits integration only very slightly, indicating that the thylakoidal delta pH does not play a significant role in the integration mechanism. In each of these respects, the requirements for CFoII integration differ notably from those determined for integration of the light-harvesting chlorophyll-binding protein of photosystem II. The integration mechanism also differs significantly from the two mechanisms involved in the translocation of lumenal proteins across the thylakoid membrane, since one of these processes requires the presence of stromal protein factors and ATP, and the other mechanism is dependent on the thylakoidal delta pH. This conclusion is reinforced by the finding that saturation of the translocation system for the precursor to the lumenal 23 kDa oxygen-evolving complex protein does not affect integration of CFoII into thylakoids.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Targeting of proteins to the thylakoids by bipartite presequences: CFoII is imported by a novel, third pathway. 813 15

Cytosol-synthesized chloroplast and mitochondrial precursor proteins are proteolytically processed after import by highly specific, metal-dependent soluble enzymes: the stromal processing peptidase (SPP) and the matrix processing peptidase (MPP), respectively. We have used in vitro processing assays to compare the reaction specificities of highly purified preparations of pea SPP and Neurospora crassa MPP, both of which are unable to cleave a variety of 'foreign' proteins. We show that SPP can cleave all five mitochondrial precursor proteins tested, namely cyclophilin, the beta subunit of the F1-ATPase complex, the Rieske FeS protein, the alpha-MPP subunit and cytochrome b2. In contrast, MPP is unable to cleave any chloroplast precursor proteins tested. Several of the mitochondrial precursor proteins are cleaved more efficiently by SPP than are many authentic chloroplast precursor proteins but, in each case, cleavage takes place at a site or sites which are N-terminal to the authentic MPP site; pre-cyclophilin is cleaved 5 residues upstream of the MPP site and the precursor of the beta subunit of the F1-ATPase complex is cleaved at sites 5 and 12 residues upstream. We discuss the implications of these data for the SPP reaction mechanism.
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PMID:Efficient but aberrant cleavage of mitochondrial precursor proteins by the chloroplast stromal processing peptidase. 816 39

We have established a homologous system for studying mitochondrial protein import in Chlamydomonas reinhardtii, using C. reinhardtii precursor proteins and mitochondria isolated from C. reinhardtii. The precursors of the F1 alpha ATP synthase subunit and the Rieske FeS protein were imported into mitochondria with high efficiency, while the F1 beta subunit precursor was imported with much lower efficiency. The import of heterologous precursor proteins from higher plants was also less efficient. The precursor of the C. reinhardtii PsaF chloroplast protein was converted into a protease-protected form upon incubation with mitochondria. In vitro processing studies revealed that in contrast to the situation in higher plants, the processing of the precursors was catalysed by a soluble, matrix-located peptidase.
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PMID:Homologous and heterologous protein import into mitochondria isolated from the green alga Chlamydomonas reinhardtii. 942 17

Nuclear-encoded mitochondrial precursor proteins are proteolytically processed inside the mitochondrion after import. The general mitochondrial processing activity in plant mitochondria has been shown to be integrated into the cytochrome bc1 complex of the respiratory chain. Here we investigate the occurrence of an additional, matrix-located processing activity by incubation of the precursors of the soybean mitochondrial proteins, alternative oxidase, the FAd subunit of the ATP synthetase and the tobacco F1 beta subunit of the ATP synthase, with the membrane and soluble components of mitochondria isolated from soybean cotyledons and spinach leaves. A matrix-located peptidase specifically processed the precursors to the predicted mature form in a reaction which was sensitive to orthophenanthroline, a characteristic inhibitor of mitochondrial processing peptidase (MPP). The specificity of the matrix peptidase was illustrated by the inhibition of processing of the alternative oxidase precursor in both soybean and spinach matrix extracts upon altering a single amino acid residue in the targeting presequence (-2 Arg to Gly). Additionally, there was no evidence for general proteolysis of precursor proteins incubated with the matrix. The purity of the matrix fractions was ascertained by spectrophotometric and immunological analyses. The results demonstrate that there is a specific processing activity in the matrix of soybean and spinach in addition to the previously well characterized membrane-bound MPP integrated into the cytochrome bcl complex of the respiratory chain.
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PMID:A matrix-located processing peptidase of plant mitochondria. 948 72

The plastids found in diatoms and other chromophytic algae are completely enclosed by four membranes in contrast to chloroplasts of higher plants, which are surrounded by only two membranes. The bipartite targeting sequence of diatom nuclear-encoded plastid proteins contains an endoplasmic reticulum signal sequence and, based on sequence comparison, a transit peptide-like domain similar to that which targets proteins into the plastids of higher plants. By performing heterologous import experiments using the precursor of the gamma subunit of the chloroplast ATPase from the diatom Odontella sinensis we were able to show that protein import into diatom plastids is at least a two-step event. We demonstrate that the first step involves co-translational transport through endoplasmic reticulum membranes and that there is an additional targeting step which is similar to the import of precursor proteins into chloroplasts of higher plants and green algae indicating that the transit peptide-like domain of the diatom precursor is functionally equivalent to the respective targeting signal of higher plants. Our results suggest that the transit peptide depending targeting mechanism in plastids has apparently remained relatively unchanged over the course of evolution, with only the peptidase cleavage site significantly modified.
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PMID:Protein transport into "complex" diatom plastids utilizes two different targeting signals. 981 93

Chlamydomonas reinhardtii mutants defective in the chloroplast ATP synthase are highly sensitive to light. The ac46 mutant is affected in the MDH1 gene, required for production or stability of the monocistronic atpH mRNA encoding CF(O)-III. In this and other ATP synthase mutants, we show that short-term exposure to moderate light intensities-a few minutes-induces an inhibition of electron transfer after the primary quinone acceptor of photosystem II (PSII), whereas longer exposure-several hours-leads to a progressive loss of PSII cores. An extensive swelling of thylakoids accompanies the initial inhibition of electron flow. Thylakoids deflate as PSII cores are lost. The slow process of PSII degradation involves the participation of ClpP, a chloroplast-encoded peptidase that is part of a major stromal protease Clp. In the light of the above findings, we discuss the photosensitivity of ATP synthase mutants with respect to the regular photoinhibition process that affects photosynthetic competent strains at much higher light intensities.
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PMID:The light sensitivity of ATP synthase mutants of Chlamydomonas reinhardtii. 1135 Nov 4

The generation of cellular energy depends on the coordinated assembly of nuclear and mitochondrial-encoded proteins into multisubunit respiratory chain complexes in the inner membrane of mitochondria. Here, we describe the identification of a conserved metallopeptidase present in the intermembrane space, termed Atp23, which exerts dual activities during the biogenesis of the F(1)F(O)-ATP synthase. On one hand, Atp23 serves as a processing peptidase and mediates the maturation of the mitochondrial-encoded F(O)-subunit Atp6 after its insertion into the inner membrane. On the other hand and independent of its proteolytic activity, Atp23 promotes the association of mature Atp6 with Atp9 oligomers. This assembly step is thus under the control of two substrate-specific chaperones, Atp10 and Atp23, which act on opposite sides of the inner membrane. Strikingly, both ATP10 and ATP23 were found to genetically interact with prohibitins, which build up large, ring-like assemblies with a proposed scaffolding function in the inner membrane. Our results therefore characterize not only a novel processing peptidase with chaperone activity in the mitochondrial intermembrane space but also link the function of prohibitins to the F(1)F(O)-ATP synthase complex.
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PMID:Prohibitins interact genetically with Atp23, a novel processing peptidase and chaperone for the F1Fo-ATP synthase. 1713 88


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