Reconstitution of the membrane-bound, ubiquinone-dependent pyruvate oxidase respiratory chain of Escherichia coli with the cytochrome d terminal oxidase
Pyruvate oxidase is a flavoprotein dehydrogenase located on the inner surface of the Escherichia coli cytoplasmic membrane and coupled to the E. coli aerobic respiratory chain. The role of quinones in the pyruvate oxidase system is investigated, and a minimal respiratory chain is described consisting of only two pure proteins plus ubiquinone 8 incorporated in phospholipid vesicles. The enzymes used in this reconstitution are the flavorprotein and the recently purified E. coli cytochrome d terminal oxidase. The catalytic velocity of the reconstituted liposome system is about 30% of that observed when the flavoprotein is reconstituted with E. coli membranes. It is also shown that electron transport from pyruvate to oxygen in the liposome system generates a transmembrane potential of at least 180 mV (negative inside), which is sensitive to the uncouplers carbonyl cyanide p-(trichloromethoxy)phenylhydrazone and valinomycin. A transmembrane potential is also generated by the oxidation of ubiquinol 1 by the terminal oxidase in the absence of the flavoprotein. It is concluded that: the flavoprotein can directly reduce ubiquinone 8 within the phospholipid bilayer; menaquinone 8 will not effectively substitute for ubiquinone 8 in this electron-transfer chain; and the cytochrome d terminal oxidase functions as a ubiquinol 8 oxidase and serves as a coupling site in the E. coli aerobic respiratory chain. These investigations suggest a relatively simple organization for the E. coli respiratory chain.
- Research Organization:
- Univ. of Illinois, Urbana
- DOE Contract Number:
- AC02-80ER10682
- OSTI ID:
- 6966308
- Journal Information:
- Biochemistry; (United States), Vol. 23:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CELL MEMBRANES
BIOCHEMISTRY
ELECTRIC POTENTIAL
OXIDOREDUCTASES
BIOCHEMICAL REACTION KINETICS
BINDING ENERGY
CYTOCHROME OXIDASE
DIAPHORASE
ELECTRON TRANSFER
MEMBRANE TRANSPORT
OXYGEN
PYRUVIC ACID
RECEPTORS
UBIQUINONE
AROMATICS
BENZOQUINONES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMISTRY
COENZYMES
ELEMENTS
ENERGY
ENZYMES
HAEM DEHYDROGENASES
HETEROCYCLIC COMPOUNDS
ISOALLOXAZINES
KETO ACIDS
KINETICS
MEMBRANES
NONMETALS
NUCLEOTIDE DEHYDROGENASES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
QUINONES
REACTION KINETICS
550200* - Biochemistry