Biomaterial Database

Redox-linked proton translocation in the b-c1 complex from beef-heart mitochondria reconstituted into phospholipid vesicles. Studies with chemical modifiers of amino acid residues. 1983

M Lorusso, and D Gatti, and D Boffoli, and E Bellomo, and S Papa

Possible involvement of polypeptides of b-c1 complex of beef-heart mitochondria in its redox and protonmotive activity has been investigated, by means of chemical modification of amino acid residues in the soluble as well as in the phospholipid-reconstituted b-c1 complex. Treatment of the enzyme with tetranitromethane (C(NO2)4) or with ethoxyformic anhydride (EFA), that modify reversibly tyrosyl and hystidyl residues respectively, resulted in a marked inhibition of electron transport from reduced quinols to cytochrome c. This was accompanied, in b-c1 reconstituted into phospholipid vesicles, by a parallel inhibition of respiratory-linked proton translocation; the H+/e- stoichiometry remained unchanged. Treatment of b-c1 complex with DCCD, that specifically modifies carboxylic groups of glutammic or aspartic residues caused a marked depression of proton translocation in b-c1 vesicles, under conditions where the rate of electron flow in the coupled state, was enhanced. As a consequence the H+/e- stoichiometry was lowered. SDS gel electrophoresis and [14C]DCCD-labelling of the polypeptides of the b-c1 complex showed a major binding of 14C-DCCD to the 8-kDa subunit of the complex and possible cross-linking, induced by DCCD treatment, of polypeptide(s) in the 8-kDa band and the 12-kDa band, with the Fe-s protein of the complex, with the appearance of a new polypeptide band with an apparent molecular mass of about 40 kDa. Involvement of polypeptides of low molecular mass, for which no functional role was so far described, and possibly of the Fe-S protein in the redox-linked proton translocation in b-c1 complex is suggested.

UI	MeSH Term	Description	Entries
D008929	Mitochondria, Heart	The mitochondria of the myocardium.	Heart Mitochondria,Myocardial Mitochondria,Mitochondrion, Heart,Heart Mitochondrion,Mitochondria, Myocardial
D009097	Multienzyme Complexes	Systems of enzymes which function sequentially by catalyzing consecutive reactions linked by common metabolic intermediates. They may involve simply a transfer of water molecules or hydrogen atoms and may be associated with large supramolecular structures such as MITOCHONDRIA or RIBOSOMES.	Complexes, Multienzyme
D009247	NADH, NADPH Oxidoreductases	A group of oxidoreductases that act on NADH or NADPH. In general, enzymes using NADH or NADPH to reduce a substrate are classified according to the reverse reaction, in which NAD+ or NADP+ is formally regarded as an acceptor. This subclass includes only those enzymes in which some other redox carrier is the acceptor. (Enzyme Nomenclature, 1992, p100) EC 1.6.	Oxidoreductases, NADH, NADPH,NADPH Oxidoreductases NADH,Oxidoreductases NADH, NADPH
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D010743	Phospholipids	Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system.	Phosphatides,Phospholipid
D011522	Protons	Stable elementary particles having the smallest known positive charge, found in the nuclei of all elements. The proton mass is less than that of a neutron. A proton is the nucleus of the light hydrogen atom, i.e., the hydrogen ion.	Hydrogen Ions,Hydrogen Ion,Ion, Hydrogen,Ions, Hydrogen,Proton
D011808	Quinone Reductases	NAD(P)H:(quinone acceptor) oxidoreductases. A family that includes three enzymes which are distinguished by their sensitivity to various inhibitors. EC 1.6.99.2 (NAD(P)H DEHYDROGENASE (QUINONE);) is a flavoprotein which reduces various quinones in the presence of NADH or NADPH and is inhibited by dicoumarol. EC 1.6.99.5 (NADH dehydrogenase (quinone)) requires NADH, is inhibited by AMP and 2,4-dinitrophenol but not by dicoumarol or folic acid derivatives. EC 1.6.99.6 (NADPH dehydrogenase (quinone)) requires NADPH and is inhibited by dicoumarol and folic acid derivatives but not by 2,4-dinitrophenol.	Menaquinone Reductases,Reductases, Menaquinone,Reductases, Quinone
D002417	Cattle	Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.	Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D004024	Dicyclohexylcarbodiimide	A carbodiimide that is used as a chemical intermediate and coupling agent in peptide synthesis. (From Hawley's Condensed Chemical Dictionary, 12th ed)	DCCD
D004047	Diethyl Pyrocarbonate	Preservative for wines, soft drinks, and fruit juices and a gentle esterifying agent.	Diethyl Dicarbonate,Diethyl Oxydiformate,Pyrocarbonic Acid Diethyl Ester,Diethylpyrocarbonate,Ethoxyformic Anhydride,Anhydride, Ethoxyformic,Dicarbonate, Diethyl,Oxydiformate, Diethyl,Pyrocarbonate, Diethyl