Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.3.5.1 (succinate dehydrogenase)
 8,177 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A succinate dehydrogenase complex was isolated in a three-step purification from plasma membranes of the thermoacidophilic archaebacterium Sulfolobus acidocaldarius. It consists of four subunits: a, 66 kDa; b, 31 kDa; c, 28 kDa and d, 12.8 kDa. In the 141-kDa native protein, the four subunits are present in an equimolar stoichiometry. The complex contains acid-non-extractable flavin, iron and acid-labile sulphide. Maximal succinate dehydrogenase activities were recorded at pH 6.5, which coincides with the internal pH of Sulfolobus cells. The temperature optimum of 81 degrees C defines the Sulfolobus succinate dehydrogenase as a thermophilic enzyme complex. The Km for succinate was found to be 1.42 mM (55 degrees C). Similar to the mitochondrial soluble succinate dehydrogenase, this enzyme is capable of transferring electrons to artificial electron acceptors, for instance phenazine methosulfate, N,N,N',N'-tetramethyl-p-phenylenediamine and ferricyanide. In contrast to the mitochondrial succinate dehydrogenase, the archaebacterial enzyme reduces 1,4-dichloroindophenol also in the absence of phenazine methosulfate. Caldariella quinone, the physiological electron mediator in the Sulfolobus respiratory chain, was only slowly reduced under adjusted conditions. The succinate--phenazine methosulfate-(1,4-dichloroindophenol) oxidoreductase of the isolated complex was strongly inhibited by tetrachlorobenzoquinone. In plasma membranes the complex reduces molecular oxygen in a cyanide-sensitive reaction. Polyclonal Sulfolobus anti-a antibodies crossreacted with 66-67-kDa polypeptides from membranes of Thermoplasma acidophilium, Sulfolobus solfataricus and beef heart submitochondrial particles.
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PMID:Purification and characterisation of an archaebacterial succinate dehydrogenase complex from the plasma membrane of the thermoacidophile Sulfolobus acidocaldarius. 193 55

In maize, the functional gene encoding mitochondrial ribosomal protein S14 (rps14) has been translocated to the nucleus where it became integrated between both exons of a gene encoding the iron-sulfur subunit of succinate dehydrogenase (sdh2). Two transcripts are generated from this locus by alternative splicing. One transcript encodes a precursor for a functional SDH2 protein, while the second transcript encodes a chimeric SDH2(t)-RPS14 precursor protein. In this paper we show that the same mitochondrial targeting presequence is able to direct the import of both precursors into isolated mitochondria and is removed during import. This processing event generates a 28 kDa protein from the SDH2 precursor, which corresponds to the iron-sulfur subunit of respiratory complex II present in maize mitochondria. In addition to cleavage of the presequence, the chimeric precursor undergoes proteolytical processing between SDH2 and RPS14. This processing generates RPS14, which is found assembled into mitochondrial ribosomes, and a truncated SDH2 protein which is degraded. Therefore, our results support a role of the SDH2 domain in the chimeric precursor only in providing a mitochondrial targeting function for RPS14.
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PMID:The nuclear-encoded SDH2-RPS14 precursor is proteolytically processed between SDH2 and RPS14 to generate maize mitochondrial RPS14. 1079 6

Structure and function of chloroplasts are known to after during senescence. The senescence-induced specific changes in light harvesting antenna of photosystem II (PSII) and photosystem I (PSI) were investigated in Cucumis cotyledons. Purified light harvesting complex II (LHCII) and photosystem I complex were isolated from 6-day non-senescing and 27-day senescing Cucumis cotyledons. The chlorophyll a/b ratio of LHCII obtained from 6-day-old control cotyledons and their absorption, chlorophyll a fluorescence emission and the circular dichroism (CD) spectral properties were comparable to the LHCII preparations from other plants such as pea and spinach. The purified LHCII obtained from 27-day senescing cotyledons had a Chl a/b ratio of 1.25 instead of 1.2 as with 6-day LHCII and also exhibited significant changes in the visible CD spectrum compared to that of 6-day LHCII, indicating some specific alterations in the organisation of chlorophylls of LHCII. The light harvesting antenna of photosystems are likely to be altered due to aging. The room temperature absorption spectrum of LHCII obtained from 27-day senescing cotyledons showed changes in the peak positions. Similarly, comparison of 77K chlorophyll a fluorescence emission characteristics of LHCII preparation from senescing cotyledons with that of control showed a small shift in the peak position and the alteration in the emission profile, which is suggestive of possible changes in energy transfer within LHCII chlorophylls. Further, the salt induced aggregation of LHCII samples was lower, resulting in lower yields of LHCII from 27-day cotyledons than from normal cotyledons. Moreover, the PSI preparations of 6-day cotyledons showed Chl a/b ratios of 5 to 5.5, where as the PSI sample of 27-day cotyledons had a Chl a/b ratio of 2.9 suggesting LHCII association with PSI. The absorption, fluorescence emission and visible CD spectral measurements as well as the polypeptide profiles of 27-day cotyledon-PSI complexes indicated age-induced association of LHCII of PSII with PSI obtained from 27-day cotyledons. We modified our isolation protocols by increasing the duration of detergent Triton X-100 treatment for preparing the PSI and LHCII complexes from 27-day cotyledons. However, the PSI complexes isolated from senescing samples invariably proved to have significantly low Chl a/b ratio suggesting an age induced lateral movement and possible association of LHCII with PSI complexes. The analyses of polypeptide compositions of LHCII and PSI holocomplexes isolated from 6-day control and 27-day senescing cotyledons showed distinctive differences in their profiles. The presence of 26-28 kDa polypeptide in PSI complexes from 27-day cotyledons, but not in 6-day control PSI complexes is in agreement with the notion that senescence induced migration of LHCII to stroma lamellae and its possible association with PSI. We suggest that the migration of LHCII to the stroma lamellae region and its possible association with PSI might cause the destacking and flattening of grana structure during senescence of the chloroplasts. Such structural changes in light harvesting antenna are likely to alter energy transfer between two photosystems. The nature of aging induced migration and association of LHCII with PSI and its existence in other senescing systems need to be estimated in the future.
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PMID:Characterisation of senescence-induced changes in light harvesting complex II and photosystem I complex of thylakoids of Cucumis sativus cotyledons: age induced association of LHCII with photosystem I. 1268 33