Open AccessThe Function fo the Subunits of the Fumarate Reductase Complex of Vibrio succinogenes
Author(s) -
UNDEN Gottfried,
KRÖGER Achim
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb05739.x
Subject(s) - fumarate reductase , protein subunit , cytochrome , reductase , chemistry , cytochrome c , dimethyl fumarate , stereochemistry , succinate dehydrogenase , biochemistry , redox , enzyme , biology , mitochondrion , organic chemistry , multiple sclerosis , immunology , gene
The membrance‐bound fumarate reductase complex of Vibrio succinogenes catalyzes the reduction fo fumarate by 2,3‐dimethyl‐1,4‐naphthohydrquinone (dimethylnaphthohydroquinone) and consists of three different keptides ( M r 79000, M r 31000 and M r 25000), the smallest of which is cytochrome b [Unden, G., Hackenberg, H. and Kröger, A.(1980) Biochem. Biophys.Acta 591 , 275–288]. The complex was cleaved with guanidinium chloride, the resulting subunits characterized and their functions within the complex investigated by reconstitutional experiments.1 The M r ‐79000 subunits catalyzed the reduction fo fumarate by benzylviologen radicals as well as the oxidation of succinate by methylene blue, but not fumarate reduction by dimethylnaphthohydroquinone. 2 The spectral and the redox properties of the isolated cytochrome b ( M r 25000) were equivalent to those of the high‐protential cytochrome b of the bacteria. The isolated cytochrome b had a midpoint potential of ‐15 mV and was reducible by dimethylnaphthohydroquinone in the absence of the other subunits. 3 The M r ‐31000 subunit did not catalyze any of the ractions mentioned above. For the reduction of cytochrome b by succinate in the presence of the M r ‐79000 subunits, an amount of the M r ‐31000 subunits was required which was equimolar to cytochrome b . 4 The activity of fumarate reduction by dimethylnaphthohydroquinone could be restord by coprecipitation of the three subunits. It is concluded that the fumarate reductase complex has two different reactive sites, which are essential for its function in the phosphorylative electron transport of the bacterium. The site reacting with the substrates fumarate and succinate is situated on the M r ‐79000 subunit, and that reacting with dimethylnaphthohydroquinone is cytochrome b . The M r ‐31000 subunit mediates the electron transport between cytochrome b and the M r ‐31000 subunits mediates the electron transport between cytochrome b and the M r ‐79000 subunit.