Succinate dehydrogenase, mitochondrial iron-sulfur clusters

As indicated in Sections 1 and 2, succinate is an electron donor widely utilized for NAD(P) reduction by phototrophic purple bacteria. The membrane-bound enzyme responsible for succinate oxidation has been solubilized and partially characterized in the purple non-sulfur bacteria R. rubrum [73,74] and Rhodopseudo-monas sphaeroides (recently renamed Rhodobacter sphaeroides) [57]. In situ characterization of the iron-sulfur centers likely to be associated with succinate dehydrogenase has been accomplished for Rps. capsulata [59] and C. vinosum [51]. Of particular interest is the presence of a succinate-reducible [51,57,58,73] and fu-marate-oxidizable [51] iron-sulfur cluster with near +50 mV that, like center S-3 [60,61,75,76] of mitochondrial succinic dehydrogenase (Complex II), is paramagnetic in the oxidized state. The enzyme in phototrophic bacteria also appears to have one or two ferredoxin-like (i.e., paramagnetic in the reduced state) iron-sulfur centers that correspond to centers S-1 (succinate-reducible, EJ ranging from... 

Succinate dehydrogenase, like aconitase, is an iron—sulfur protein. Indeed, succinate dehydrogenase contains three different kinds of iron—sulfur clusters, 2Fe-2S (two iron atoms bonded to two inorganic sulfides), 3Fe-4S, and 4Fe-4S. Succinate dehydrogenase— which consists of two subunits, one 70 kd and the other 27 kd—differs from other enzymes in the citric acid cycle in being embedded in the inner mitochondrial membrane. In fact, succinate dehydrogenase is directly associated with the electron-transport chain, the link between the citric acid cycle and ATP formation. FADH2 produced by the... 

Carboxamides are a group of fungicides that control diseases caused by Basidiomycete type fungi (42). The best known member of this group is carboxin (Figure 6). Carboxamides specifically block membrane bound succinate-ubiquinone oxldoreductase activity in the mitochondrial electron transport chain (42, ). The carboxin receptor in the succinic dehydrogenase complex (SDC) is believed to be the iron-sulfur cluster Sj complexed with small coenzyme Q binding polypeptide(s) in a phospholipid environment (45.46 >. 

Succinate dehydrogenase and fumarate reductase catalyse the oxidation of succinate to fumarate and the reverse reaction, respectively. A structural comparison of the functionally related enzymes was performed for the E. coli species. One of the four units of each enzyme is an iron-sulfur subunit which contains three distinct [Fe4S4] clusters. A historical perspective of the spectroscopy of succinate dehydrogenase, which is also a part of mitochondrial complex II, has been published in which the development of the iron-sulfur clusters is described. "... 

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