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Quinone reduction sites and the role of heme in succinate:quinone reductase. Studies in Bacillus subtilis and Paracoccus denitrificans

Matsson, Mikael LU (2000)
Abstract
Succinate:quinone reductase (SQR) is an enzyme in the respiratory system of aerobic cells. SQR catalyzes two reactions, the oxidation of succinate to fumarate and the reduction of quinone to quinol. These reactions are coupled by electron transfer within the enzyme from the site of succinate oxidation to the site of quinone reduction. Some enzymes reduce ubiquinone (exergonic reaction) whereas others reduce menaquinone (endergonic reaction). SQR is composed of one membrane-peripheral domain and one membrane-anchor domain. Succinate is oxidized on the peripheral domain which is attached to the electronegative side of the respiratory membrane. This domain consists of two polypeptides, one covalently bound FAD group, one [2Fe-2S] cluster, one... (More)
Succinate:quinone reductase (SQR) is an enzyme in the respiratory system of aerobic cells. SQR catalyzes two reactions, the oxidation of succinate to fumarate and the reduction of quinone to quinol. These reactions are coupled by electron transfer within the enzyme from the site of succinate oxidation to the site of quinone reduction. Some enzymes reduce ubiquinone (exergonic reaction) whereas others reduce menaquinone (endergonic reaction). SQR is composed of one membrane-peripheral domain and one membrane-anchor domain. Succinate is oxidized on the peripheral domain which is attached to the electronegative side of the respiratory membrane. This domain consists of two polypeptides, one covalently bound FAD group, one [2Fe-2S] cluster, one [4Fe-4S] cluster and one [3Fe-4S] cluster. The anchor domain harbors the quinone reduction site(s) and is, depending on the organism, composed of one or two polypeptides and one or two b-type hemes. Succinate:menaquinone reductases contain two heme groups, one proximal heme (heme bP) located close to the negative side of the membrane and one distal heme (heme bD) located close to the positive side of the membrane. Succinate:ubiquinone reductases contain only heme bP. Electron transfer from succinate to quinone occurs in a linear pathway including the FAD, the [2Fe-2S] cluster, the [4Fe-4S] cluster, the [3Fe-4S] cluster and sometimes heme as electron carriers in the given order.



I have studied SQR from two evolutionary very distant bacteria, Bacillus subtilis and Paracoccus denitrificans. B. subtilis SQR reduces menaquinone whereas P. denitrificans SQR reduces ubiquinone. The combined experimental results support the following model. In succinate:ubiquinone reductases the quinone reduction site is located close to the [3Fe-4S] cluster on the negative side of the membrane. Heme is not required as an electron carrier in these enzymes. Ubiquinone reduction by succinate is not dependent on the transmembrane electrochemical potential. In succinate:menaquinone reductases the quinone reduction site is located close to the positive side of the membrane. Heme bP and heme bD mediate transmembrane electron transfer from the [3Fe-4S] cluster to menaquinone. The transmembrane electrochemical potential provides driving force for the endergonic reduction of menaquinone by succinate. (Less)
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author
opponent
  • Prof Guest, John R., FRS, Department of Molecular Biology and Biotechnology, University of Sheffield
organization
publishing date
type
Thesis
publication status
published
subject
keywords
carboxin, cytochrome b, electron transport, heme, quinone, Paracoccus denitrificans, Bacillus subtilis, Succinate:quinone reductase, succinate dehydrogenase, Microbiology, bacteriology, virology, mycology, Mikrobiologi, bakteriologi, virologi, mykologi
pages
48 pages
publisher
Department of Microbiology, Lund University
defense location
Blue lecture hall, Ecology building, Sölvegatan 37, Lund
defense date
2003-03-24 10:15
external identifiers
  • Other:ISRN: LUNBDS/NBNB-1036/1-48(2000)
ISBN
91-628-4021-5
language
English
LU publication?
yes
id
35b471fa-832b-4b26-a4a4-62901793dc15 (old id 40338)
date added to LUP
2007-07-31 13:45:44
date last changed
2016-09-19 08:45:08
@misc{35b471fa-832b-4b26-a4a4-62901793dc15,
  abstract     = {Succinate:quinone reductase (SQR) is an enzyme in the respiratory system of aerobic cells. SQR catalyzes two reactions, the oxidation of succinate to fumarate and the reduction of quinone to quinol. These reactions are coupled by electron transfer within the enzyme from the site of succinate oxidation to the site of quinone reduction. Some enzymes reduce ubiquinone (exergonic reaction) whereas others reduce menaquinone (endergonic reaction). SQR is composed of one membrane-peripheral domain and one membrane-anchor domain. Succinate is oxidized on the peripheral domain which is attached to the electronegative side of the respiratory membrane. This domain consists of two polypeptides, one covalently bound FAD group, one [2Fe-2S] cluster, one [4Fe-4S] cluster and one [3Fe-4S] cluster. The anchor domain harbors the quinone reduction site(s) and is, depending on the organism, composed of one or two polypeptides and one or two b-type hemes. Succinate:menaquinone reductases contain two heme groups, one proximal heme (heme bP) located close to the negative side of the membrane and one distal heme (heme bD) located close to the positive side of the membrane. Succinate:ubiquinone reductases contain only heme bP. Electron transfer from succinate to quinone occurs in a linear pathway including the FAD, the [2Fe-2S] cluster, the [4Fe-4S] cluster, the [3Fe-4S] cluster and sometimes heme as electron carriers in the given order.<br/><br>
<br/><br>
I have studied SQR from two evolutionary very distant bacteria, Bacillus subtilis and Paracoccus denitrificans. B. subtilis SQR reduces menaquinone whereas P. denitrificans SQR reduces ubiquinone. The combined experimental results support the following model. In succinate:ubiquinone reductases the quinone reduction site is located close to the [3Fe-4S] cluster on the negative side of the membrane. Heme is not required as an electron carrier in these enzymes. Ubiquinone reduction by succinate is not dependent on the transmembrane electrochemical potential. In succinate:menaquinone reductases the quinone reduction site is located close to the positive side of the membrane. Heme bP and heme bD mediate transmembrane electron transfer from the [3Fe-4S] cluster to menaquinone. The transmembrane electrochemical potential provides driving force for the endergonic reduction of menaquinone by succinate.},
  author       = {Matsson, Mikael},
  isbn         = {91-628-4021-5},
  keyword      = {carboxin,cytochrome b,electron transport,heme,quinone,Paracoccus denitrificans,Bacillus subtilis,Succinate:quinone reductase,succinate dehydrogenase,Microbiology,bacteriology,virology,mycology,Mikrobiologi,bakteriologi,virologi,mykologi},
  language     = {eng},
  pages        = {48},
  publisher    = {ARRAY(0x921b770)},
  title        = {Quinone reduction sites and the role of heme in succinate:quinone reductase. Studies in Bacillus subtilis and Paracoccus denitrificans},
  year         = {2000},
}