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THE PROTON PORE IN THE ESCHERICHIA-COLI f0f1-ATPASE - SUBSTITUTION Of GLUTAMATE BY GLUTAMINE AT POSITION-219 Of THE A-SUBUNIT PREVENTS f0-MEDIATED PROTON PERMEABILITY

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BIOCHIMICA ET BIOPHYSICA ACTA 1988年第2期933卷 241-248页

作者： LIGHTOWLERS, RN HOWITT, SM HATCH, L GIBSON, f COX, G Department of Biochemistry John Curtin School of Medical Research Canberra City ACT 2601 Australia

Three mutations in the uncB gene encoding the .alpha.-subunit of the f0 portion of the f0f1-ATPase of Escherichia coli were produced by site-directed mutagenesis. These mutations directed the substitution of Glu-219 by Gln, or of Lys-203 by Ile, or of Glu-196 by Ala. Strains carrying either the Lys-203 or Glu-196 substitutions showed growth characteristics indistinguishable from the coupled control strain. Properties of membrane preparations from these strains were also similar to those from the coupled control strain. The substitution of Glu-219 by Gln resulted in a strain which was unable to utilise succinate as sole carbon source and had a growth-yield characteristic of an uncoupled strain. Membrane preparations of the Glu-219 mutant were proton impermeable and the f1-ATPase activity was inhibited by about 50% when membrane-bound. The results are discussed with reference to a previously proposed intramembranous proton pore involving subunits a and c.

关键词： ATPase, f 0 f 1 - Proton channel Site directed mutagenesis Proton permeability ( E. coli ) DCCD N , N ′-dicyclohexylcarbodiimide

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COMPARATIVE METABOLISM Of PHENANTHRENE AND BENZO[f]QUINOLINE BY RAT-LIVER MICROSOMES

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CANCER LETTERS 1988年第3期43卷 197-205页

作者： KANDASWAMI, C KUMAR, S RUTKOWSKI, JP SIKKA, HC SUNY COLL BUFFALO GREAT LAKES LAB 1300 ELMWOOD AVE BUFFALO NY 14222 USA

The metabolism of benzo[f]quinoline (BfQ) and its carbon analog phenanthrene has been compared in incubations with liver microsomes from control, 3-methylcholanthrene (3-MC)- and phenobarbital (PB)-pretreated rats. The rates of phenanthrene metabolism by the three types of microsomes were 0.7, 4.1 and 1.5 nmol/mg protein per min, respectively;the values for BfQ were 0.5, 3.7 and 2.5, respectively. Besides N-oxidation, the metabolism of BfQ by all the above microsomes was almost exclusively at the benzo-ring (49-69%) while that of phenanthrene was predominantly at the K-region (50-71%). Phenanthrene-1,2-dihydrodiol, a precursor of the bay-region diol epoxide of phenanthrene, was produced many times more than phenanthrene-3,4-dihydrodiol by both 3-MC- and PB-induced microsomes. While BfQ-7,8-dihydrodiol, the precursor of the bay-region diol epoxide of BfQ, was the predominant metabolite with 3-MC-induced microsomes, it was a minor metabolite with PB-induced microsomes. The benzo-ring oxidation of BfQ, but not of phenanthrene, was position-specific, i.e. predominantly 7,8-oxidation by 3-MC-induced microsomes and 9,10-oxidation by PB-induced microsomes, and implies that aza-substitution results in a site-specific attack by different cytochromes P-450.

关键词： benzo[ f ]quinoline phenanthrene aza-polynuclear aromatic hydrocarbon aza-arene nitrogen heterocyclic

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HEPATIC DNA ADDUCT fORMATION IN RATS TREATED WITH BENZO[f]QUINOLINE

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CANCER LETTERS 1988年第1-2期43卷 133-138页

作者： SIKKA, HC KANDASWAMI, C KUMAR, S RUTKOWSKI, JP DUBEY, SK EARLEY, K GUPTA, RC BAYLOR COLL MED DEPT PHARMACOL HOUSTON TX 77030 USA

The formation of hepatic DNA adducts in male Sprague-Dawley rats following i.p. administration of benzo[f]quinoline (BfQ) was examined using a 32P-post-labeling assay. BfQ exhibited a low binding (11-27 amol adducts/.mu.g DNA) to liver DNA. Two BfQ-nucleoside adducts (one major and one minor) were detected. The BfQ-DNA adducts formed in vivo were chromatographically distinct from the adducts formed by the reaction of calf thymus DNA in vitro with BfQ-5,6-oxide, ***.,***.-***., ***.-epoxy-7,8,9,10-tetrahydroBfQ, ***., ***.-***.,***.-epoxy-7,8,9,10-tetrahydroBfQ, or ***.,***.-***.,***.-epoxy-7,8,9,10-tetrah-hydroBfQ-N-oxide. These results suggest that the bay-region diol epoxide of BfQ, unlike the bay-region diol epoxide derivatives of polynuclear aromatic hydrocarbons, is not involved in the covalent binding of BfQ to DNA.

关键词： benzo[ f ]quinoline aza-polynuclear aromatic hydrocarbons DNA adducts, bay-region diol epoxide

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DNA ADDUCT fORMATION Of THE CARCINOGEN 2-AMINO-3-METHYLIMIDAZO[4,5-f]-QUINOLINE IN TARGET TISSUES Of THE f-344-RAT

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CANCER LETTERS 1988年第3期41卷 345-352页

作者： SCHUT, HAJ PUTMAN, KL RANDERATH, K BAYLOR COLL MED DEPT PHARMACOL HOUSTON TX 77030 USA

2-Amino-3-methylimidazo[4,5-f]quinoline (IQ), a potent bacterial mutagen present in broiled sardines, cooked beef and beef extract, is a carcinogen in the f-344 rat, affecting mainly the liver and small and large intestines. Using 32P-postlabeling assays, the formation of IQ-DNA adducts was examined in male f-344 rats. Twenty-four hours after i.p. doses (5-50 mg IQ/kg) the liver, small and large intestine each showed the presence of 5 adducts, the liver and large intestine having an average of 18.1 and 2.4 times as many adducts, respectively, as the small intestine. None of these adducts could be detected in vehicle-treated animals. It is concluded that IQ forms specific DNA adducts in target tissues of the f-344 rat.

关键词： 2-Amino-3-methylimidazo[4,5- f ]quinoline DNA adducts 32 P-postlabeling fischer-344 rats food mutagens Heterocyclic amines

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INHIBITION Of ELECTRON-TRANSfER AND THE ELECTROGENIC REACTION IN THE CYTOCHROME B/f COMPLEX BY 2-NORMAL-NONYL-4-HYDROXYQUINOLINE N-OXIDE (NQNO) AND 2,5-DIBROMO-3-METHYL-6-ISOPROPYL-P-BENZOQUINONE (DBMIB)

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BIOCHIMICA ET BIOPHYSICA ACTA 1988年第2期933卷 258-268页

作者： JONES, RW WHITMARSH, J UNIV ILLINOIS DEPT PLANT BIOL USDA ARS URBANA IL 61801 USA

We investigated the interaction between the cytochrome b/f complex and plastoquinone by determining the effect of the electron transport inhibitors 2-n-nonyl-4-hydroxy-quinoline N-oxide (NQNO) and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) on the flash-induced turnover of cytochromes b6 and f, on the slow phase of the electrogenic reaction (515s) and on steady-state electron transport. The experiments were performed using thylakoid membranes in the presence of duroquinol, methyl viologen, and diuron, conditions in which electron transport is driven by Photosystem I and includes the cytochrome b/f complex. The data from these experiments indicate that NQNO and DMBIB inhibit at two different sites on the cytochrome b/f complex. The data can be accommodated by a modified Q-cycle in which the primary site of inhibition by NQNO is the quinone reductase site (Qc) and the primary site of DBMIB inhibition is the quinol oxidase site (Qz). NQNO is envisioned to inhibit the oxidation of the cytochrome b6-heme located nearest the outer aqueous phase, as well as to slow electron transfer between the two b-hemes. The effect of NQNO on the 515s supports the notion that the slow electrogenic reaction is due to electron transfer between the two cytochrome b6-hemes, followed by a reaction associated with plastoquinone reduction at the Qc-site (Jones and Whitmarsh (1985) Photobiochem. Photobiophys. 9, 119-127). The results indicate that the Qz-site and Qc-site are likely separated by 70% of the dielectrically weighted distance across the membrane. At low concentrations of DBMIB the kinetics of the 515s and cytochrome b6 reduction are monophasic, indicating that DMBIB moves from one inhibitory site to another within the turnover time of the cytochrome b/f complex. This observation suggests that the debinding rate of DBMIB on the extent of cytochrome f oxidation and the rate of cytochrome f reduction, raises the possibility that DBMIB has a second lower affinity binding sit

关键词： Cytochrome b f complex Electron transport inhibition Slow electrogenic step Binding site C 50 the concentration of inhibitor required to give 50% of the maximum inhibitory effect cytochrome b f complex plastoquinol-plastocyanin oxidoreductase complex DBMIB 2,5-dibromo-3-methyl-6-isopropyl- p -benzoquinone DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea DQH 2 duroquinol HQNO 2- n -heptyl-4-hydroxyquinoline N -oxide I 50 the concentration of inhibitor required for 50% inhibition of the control signal NQNO 2- n -nonyl-4-hydroxyquinoline N -oxide P-700 + the oxidized primary electron donor of Photosystem I Tricine N -[2-hydroxy-1,1-bis(hydroxymethyl)-ethyl]glycine UHDBT 5-( n -undecyl)-6-hydroxy-4,7-dioxobenzothiazole Q c putative quinone binding site on the cytochrome b f complex located near the outer aqueous phase (stroma) Q z putative quinol binding site on the cytochrome b f complex located near the inner aqueous phase (lumen) 515 s the slow phase of the electrochromic shift (rise time 3–5 ms) Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid Tricine N -[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine

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THE LOW-POTENTIAL ELECTRON-TRANSfER CHAIN IN THE CYTOCHROME B/f COMPLEX

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BIOCHIMICA ET BIOPHYSICA ACTA 1988年第2期933卷 319-333页

作者： JOLIOT, P JOLIOT, A Institut de Biologie Physico-Chimique Paris France

The oxidized-minus-reduced spectra of the low- and high-potential cytochromes b6 were measured from 380 to 590 nm under anaerobic conditions in a mutant of Chlorella sorokiniana lacking of Photosystem II (PS II). The two spectra are similar in the Soret band;in the .alpha.-band, cytochrome b1 and cytochrome bh peak at 563.4 and 564 nm, respectively. The spectrum of a third component, G, located on the outer face of the membrane and able to exchange electrons with cytochrome bh (Lavergne, J. (1983) Biochim. Biophys. Acta 725, 25-33) was characterized. The oxidized minus-reduced spectrum of G displays a negative band peaking around 424 nm (probably a double peak) and a broad and small negative band in the green region. This spectrum resembles that of a soluble high-spin cytochrome c'', as characterized in several classes of photosynthetic bacteria. As other cytochromes c'', G binds CO with a low affinity, which inhibits electron exchange with cytochrome bh. The kinetics of reduction of cytochrome bh and cytochrome b1 were measured in algae under conditions, following illumination by weak continuous light or saturating flashes. from the kinetic behaviour, the difference between the midpoint potentials of cytochrome bh and cytochrome b1 was estimated at approx. 140 mV. Two populations can be distinguished among cytochrome b/f complexes. In a first fraction, the complexes are associated with the carrier G, which very likely takes part in an electron-transfer chain mediating cytochrome b reduction by a stromal reductant. This chain could be involved in cyclic electron flow around Photosystem I. In the second fraction, where G is not attached to the complex, the reduction of the b-cytochromes is a much slower process. Cytochrome bh and G are in equilibrium, the midpoint potential G being approx. 20 mV higher than that of cytochrome bh. from the study of the PS II-driven photoreduction of cytochrome bh and G (under aerobic conditions) in a mutant which lacks of PS I, we con

关键词： Electron transfer Cytochrome b f complex Cytochrome b Cytochrome c ′ Plastoquinone ( Chlorella ) PS Photosystem PQ plastoquinone PQH 2 plastoquinol PQ − plastosemiquinone DNP-INT dinitrophenylether iodonitrothymol DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea cytochrome b cytochrome b 6 PMS N -methylphenazonium methosulphate

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RESONANCE RAMAN-SPECTROSCOPY INDICATES A LYSINE AS THE 6TH IRON LIGAND IN CYTOCHROME-f

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BIOCHIMICA ET BIOPHYSICA ACTA 1988年第1期936卷 61-66页

作者： DAVIS, DJ fRAME, MK JOHNSON, DA University of Arkansas Fayetteville AR U.S.A.

The resonance Raman spectrum of turnip cytochrome f is similar to that of other c-type cytochromes with the exception of a single band at 1532 cm-1 which is shifted to lower frequency relative to its position (1542-1545 cm-1) in other c-type cytochromes. Comparison of the frequency of this band with that in alkylated cytochrome c at high pH suggests that the sixth heme iron ligand in cytochrome f is a deprotonated lysine amino group rather than a methionine sulfur. Comparison of the amino-acid sequences of cytochromes f and c1 suggests lysine-145 as a likely candidate for the sixth heme iron ligand in cytochrome f.

关键词： Cytochrome f Raman spectroscopy Heme iron ligand

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SYNTHESIS Of A PHOTOAffINITY-SPIN-LABELED DERIVATIVE Of ATP AND ITS 1ST APPLICATION TO f1-ATPASE

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fEBS LETTERS 1988年第2期227卷 107-109页

作者： VOGELCLAUDE, P SCHAfER, G TROMMER, WE UNIV KAISERSLAUTERN FACHBEREICH CHEMERWIN SCHRODINGER STRD-6750 KAISERSLAUTERNFED REP GER MED HSCH LUBECK INST BIOCHEMD-2400 LUBECKFED REP GER

The synthesis of an ATP derivative is described, in which a spin-label is attached to the 3′-position of the ribose moiety and an azido group to C8 of the adenine ring (SL-N 3 -ATP). Irradiation of this compound at 350 nm generates a nitrene, which will react with any functional group in its vicinity. SL-N 3 -ATP exhibits a strongly immobilized ESR spectrum in a complex with f 1 -ATPase from beef heart mitochondria. It was covalently incorporated into this enzyme. SL-N 3 -ATP may be employed in ESR investigations under conditions in which non-covalent interactions are too weak for motionally restricted species to be easily observed.

关键词： f 1 -ATPase Spin-labeled ATP Photoaffinity-spin-labeled ATP N 3 -ATP the 8-azido derivative of ATP SL-ATP or SL-N 3 -ATP C3′-(2,2,5,5-tetramethyl-3-pyrroline-1-oxyl-3-carboxylic acid ester) of ATP and N 3 -ATP, respectively HPLC high-performance liquid chromatography TLC thin-layer chromatography

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MODULATION Of THE MUTAGENIC EffECTS Of 2-AMINO-3-METHYLIMIDAZO[4,5-f]QUINOLINE (IQ) AND 2-AMINO-3,4-DIMETHYLIMIDAZO[4,5-f]QUINOLINE (MEIQ) IN BACTERIA WITH RAT-LIVER 9000 X G SUPERNATANT OR MONOLAYERS Of RAT HEPATOCYTES AS AN ACTIVATION SYSTEM

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MUTATION RESEARCH 1988年第1期197卷 39-49页

作者： HOLME, JA BRUNBORG, G ALEXANDER, J TRYGG, B BJORNSTAD, C NATL INST PUBL HLTH DEPT TOXICOL GEITMYRSVEIEN 75 N-0462 OSLO 4 NORWAY

An in vitro protocol was designed to separate the process of metabolic activation from the mutational events. Cultured rat hepatocytes were first incubated with the foood mutagens 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) or 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ). After the incubation period the medium was removed and further incubated with Salmonella typhimurium TA98. A high direct mutagenic activity of the culture medium was then measured. The half-lives of the mutagenic metabolites formed form IQ and MeIQ were in the order of 45 min. The presence of the cytochrome P450 inhibitors .alpha.-naphthoflavone and metyrapone during the pre-incubation period reduced the accumulation of mutagenic metabolites. No effects of ascorbate on the mutagenic effects of IQ and MeIQ were seen. (+)-Catechin, another antioxidant and free-radical scavenger, markedly enhanced the number of IQ/MeIQ-induced revertants when added to the hepatocytes. In contrast, (+)-catechin clearly decreased the number of revertants when 9000 .times. g supernatant from rat liver (s9) was used as an activation system. No marked effect of pentachlorophenol, an inhibitor of hepatocyte sulfation and bacterial O-acetylation, was seen using hepatocytes as an activation system, while the mutagenic activity of both IQ and MeIQ was reduced by 90% in the S9/Salmonella system. The addition of an inhibitor of glucuronidation, galactosamine, or the nucleophile glutathine caused no or only minor decrease in the genotoxic effects of the IQ compounds. With both S9 and hepatocytes as activation systems the relative mutagenic effects observed in the S. typhimurium strains TA98 and TA98 NR were in the same order of magnitude, while a large decrease was seen with TA98/1,8-DNP6. The results show that this in vitro test protocol may be useful as a tool to study mechanisms involved in the formation of mutagenic metabolites.

关键词： Mutagenic activation Heterocyclic aromatic amines Hepatocytes Carcinogens Mutagens IQ MeIQ Asc ascorbate ANf α-naphthoflavone CAT (+)-catechin DMSO dimethyl sufoxide 1,8-DNP 1,8-dinitropyrene GAL galactosamine GSH glutathione HAR harmine IQ 2-amino-3-metylimidazo[4,5- f ]quinoline MeIQ 2-amino-3,4-dimethylimidazo[4,5- f ]quinoline MET metyrapone S9 9000 × g supernatant from rat-liver homogenate UDPGA uridine diphosphoglucuronic acid

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PURIfICATION Of THE H+-ATPASE fROM RHODOBACTER-CAPSULATUS, IDENTIfICATION Of THE f1f0 COMPONENTS AND RECONSTITUTION Of THE ACTIVE ENZYME

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BIOCHIMICA ET BIOPHYSICA ACTA 1988年第2期934卷 227-234页

作者： GABELLINI, N GAO, Z ECKERSKORN, C LOTTSPEICH, f OESTERHELT, D Max-Planck-Institut für Biochemie Martinsried F.R.G.

A simple method has been adopted for the isolation of the H+-ATPase from cell membranes of Rhodobacter capsulatus that is based on octylglucoside solubilization. The highly purified f0f1 enzyme catalyzes ATP hydrolysis and DCCD-sensitive ATP-Pi exchange. The isolated complex consists of nine different polypeptides with apparent molecular masses of 50, 45, 34, 29, 23, 20, 18.5, 11 and 7.5 kDa. The N-terminal sequence of the eight largest subunits were determined by automated Edman degradation. The five f1 polypeptides could be readily identified by their homology to the f1 subunits .alpha., .beta., .gamma., .delta. and .epsilon. from other Rhodospirillaceae. In contrast to prokaryotic f0 complexes known today, the membrane portion of H+-ATPase from R. capsulatus was found to be composed of four polypeptides. Three of these correspond to subunit a, b and c of the Escherichia coli enzyme (29, 18.5 and 7.5 kDa). A fourth subunit of 23 kDa may be also related to subunit b. The ATP-synthase of this photosynthetic bacterium is in this respect similar to that of chloroplasts.

关键词： ATPase purification, H + - f 0 f 1 Enzyme reconstitution ( Rb. capsulatus ) SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis DCCD N , N ′-dicyclohexylcarbodiimide fCCP carbonylcyanide p -(trifluoromethoxy)-phenylhydrazone octylglucoside n -octyl-β-D-glucopyranoside Triton X-100 octylphenoxypoly(ethoxyethanol) Tricine N -[2-hydroxy-1,1-(bis(methyl)ethyl]glycine DTT dithiothreitol EDTA ethylene dinitrile tetra acetic acid HPLC high performance liquid chromatography P i inorganic phosphate

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