Hepatotoxicity and accelerated fibrosis following 3,4-methylenedioxymetamphetamine ("ecstasy") usage.

3,4-Methylenedioxymetamphetamine ("ecstasy") has previously been reported to cause an acute hepatitis that may progress to liver failure. We present the first recorded case of ecstasy-induced accelerated hepatic fibrosis.

Psychopathology and anger in interpersonal violence offenders.

The current literature on psychopathology and anger suggests that both contribute to interpersonal violence. The present study examined psychopathology and anger expression with two objectives: to confirm previous distinctions of personality type among abusive individuals and to examine the relation between these types and anger. Cluster analysis was conducted with data gathered from 40 subjects. Results suggested confirmation of four clusters of interpersonal violence offenders. Furthermore, the most pathological cluster type reported the highest level of total anger experience, while the histrionic cluster type reported the lowest anger expression. These results provide tentative support for a positive relationship between psychopathology and anger, as well as for the distinction between overcontrolled and under-controlled anger as subtypes of interpersonal violence offenders.

Relationship of the oxidation state of the iron-sulfur cluster of aconitase to activity and substrate binding.

It is known that aconitase from mammalian mitochondria is only partially active as isolated but may be activated by incubation with iron, ascorbate, and a thiol, or with dithionite. It has been suggested that the added Fe in the activation mixture is essential for activation and that it is incorporated in the enzyme [Villafranca, J. J., & Mildvan, A. S. (1971) J. Biol. Chem. 246, 772-779; Gawron, O., Waheed, A., Glaid, A. J., & Jaklitsch, A. (1974) Biochem. J. 139, 709-714]. However, it is shown in this paper that, when the enzyme has a full complement of 3Fe and 3S, full activation is reached coulometrically, without iron or other chemical reducing agents. It is clear, therefore, that the role of activators is to reduce the iron--sulfur cluster of the enzyme. The appearance of catalytic activity on reduction of the cluster shows a pronounced lag, as does the decay of activity after reoxidizing the cluster. This suggests that catalytic activity requires a conformational change in the protein which is initiated by reduction of the cluster and that, following reoxidation, activity disappears only after the inactive conformation is assumed. Citrate and the competitive inhibitor trans-aconitate are bound to a comparable extent to the active and inactive forms, but only the active form can bind 1-hydroxy-2-nitro-1,3-propanedicarboxylic acid, a transition-state analogue. This is interpreted to show that in the inactive state aconitase cannot enter the conformation it assumes in the transition state during catalysis.

Reaction site of carboxanilides and of thenoyltrifluoroacetone in complex II.

Oxathiin carboxanilides are systemic fungicides that inhibit the oxidation of succinate by interrupting electron transport between succinate dehydrogenase [succinate:(acceptor) oxidoreductase, EC 1.3.99.1] and coenzyme Q. Kinetic and electron paramagnetic resonance studies have established that the specific binding site of carboxanilides and of thenoyltrifluoroacetone responsible for the inhibition is the same. Although the binding of carboxanilides to membrane preparations of the dehydrogenase is very tight (Ki = 0.01-0.1 microM), it is noncovalent. Identification of the membrane component(s) to which specific binding occurs has therefore required the introduction of a photoaffinity label onto the carboxanilide molecule. By using [G-3H]3'-azido-5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxanilide, it was found, in accord with earlier data with other carboxanilides, that unresolved complex II specifically binds about 0.6 mol of the inhibitor per mol of succinate dehydrogenase in equilibrium dialysis experiments. The resolved components of the complex, succinate dehydrogenase and the two binding peptides CII-3 and CII-4, failed to bind the inhibitor; however, when these were recombined with reconstitution of coenzyme Q reductase activity, the initial binding titer was restored. Azidocarboxanilide-inhibited complex II was irradiated to generate covalent linkages with the binding site, and the components of the complex were separated on polyacrylamide gel. Most of the specifically bound inhibitor was found in the low molecular weight binding peptides and phospholipids.

Characterization of the iron-sulfur centers in succinate dehydrogenase.

Two techniques have been applied to the determination of the number and type (2-Fe, 4-Fe) of iron-sulfur centers in the iron-sulfur flavoprotein succinate dehydrogenase [succinate:(acceptor) oxidoreductase, EC 1.3.99.1]. One procedure uses p-CF3C6H4SH as an extrusion reagent and Fourier transform 19F nuclear magentic resonance as the method of detection and quantitation of extruded cores of these centers in the form of [Fe2S2(SRF)4]2- and [Fe4S4(SRF)4]2- (RF = p-C6H4CF3). The second procedure, interprotein core transfer, involves thiol displacement of iron-sulfur cores followed by specific core transfer to the apoproteins of Bacillus polymyxa ferredoxin and adrenodoxin. Detection and quantitation are accomplished by electron paramagnetic resonance of reduced proteins at low temperatures. Both procedures clearly show that succinate dehydrogenase contains two dimeric (Fe2S2) and one tetrameric (Fe4S4) centers per mole of histidyl flavin, accounting for all eight nonheme iron and eight labile sulfur atoms found by chemical analysis. These results remove uncertainties created by the less than stoichiometric amounts of binuclear centers detected by electron paramagnetic resonance after dithionite reduction and provide secure characterization of the iron-sulfur centers in this enzyme.

The high potential iron-sulfur cluster of aconitase is a binuclear iron-sulfur cluster.

It has been reported (Ruzicka, F.J., and Beinert, H. (1978) J. Biol. Chem. 253, 2514-2517) that aconitase in the oxidized state, as isolated, shows an electron paramagnetic resonance signal centered at g = 2.01, typical of high potential iron-sulfur proteins. Since the magnetic state corresponding to this signal has thus far only been found in tetranuclear iron-sulfur clusters in model compounds and proteins, it could be expected that aconitase also contains a [4Fe-4S] cluster. We show here that core extrusion, in the presence of hexamethylphosphoramide and o-xylyl-alpha,alpha'-dithiol and subsequent ligand exchange with p-trifluoromethylbenzenethiol yield absorption spectra typical of binuclear iron-sulfur clusters. According to the absorbance measured, the concentration of the extruded [2Fe-2S] cluster quantitatively accounts for the iron-sulfur content of the preparations examined. Preliminary studies of the 19F nuclear magnetic resonance spectrum obtained on extrusion with p-trifluoromethylbenzenethiol confirm the presence of a binuclear cluster in aconitase.

Isolation of reconstitutively active succinate dehydrogenase in highly purified state.

Existing procedures for the isolation of mammalian succinate dehydrogenase yield preparations of high purity or retain reconstitution activity, but not both. A new procedure is described for the isolation in good yield of virtually homogeneous preparations with full reconstitution activity, and retaining iron-sulfur center 3 and the "low Km" reaction site of ferricyanide. On reincorporation of the soluble enzyme into alkali-treated membranes, the same high turnover number (approximately 21,000/min at 38 degrees) is obtained in catalytic assays as with intact inner membrane preparations.