Taxonomic changes in the genus Diabrotica Chevrolat (Coleoptera: Chrysomelidae: Galerucinae): results of a synopsis of North and Central America Diabrotica species

The following new synonyms in Diabrotica Chevrolat 1836 are proposed: D.flaviventris Jacoby 1887 and D. tibialis Jacoby 1887 are synonyms of D. adelpha Harold 1875; D. peckii Bowditch 1911 is a synonym of D. bioculata Bowditch 1911; D. nummularis Harold 1877 is a synonym of D. circulata Harold 1875; D. linensis Bechyné 1956 is a synonym of D. trifurcata Jacoby 1887; D. brunneosignata Jacoby 1887 is a synonym of D. sinuata Olivier 1790; D. duplicata Jacoby 1887 is a synonym of D. viridifasciata Jacoby 1887. Diabrotica cyaneomaculata Jacoby 1887 does not share the synapomorphies of Diabrotica and is treated as incertae sedis. Diabrotica tripunctata (Fabricius) is removed from synonymy with D. sinuata Olivier and is considered to be a valid species. The original combination is restored for Diabroticafasciata Kirsch, the species being transferred from Paranapiacaba Bechyné back to Diabrotica. It was found that the type series of D. godmani Jacoby contains seven different taxa: one is D. godmani itself; one is D. championi Jacoby; one is D. quadricollis Jacoby; three are unidentified Diabrotica species, each different from the others; and one is not a Diabrotica. The type series of D. viridicollis Jacoby contains four different taxa, D. viridicollis Jacoby itself and three different unidentified Diabrotica species.

Characterization of mass-labeled [13C14]-decabromodiphenylethane and its use as a surrogate standard in the analysis of sewage sludge samples

Very little data is available about the presence of the brominated flame retardant, DBDPE, in the environment. This study reports the characterization of [(13)C(14)]-decabromodiphenylethane and the use of this surrogate standard to positively identify and quantify the presence of DBDPE in sewage sludge samples. The large difference in response factors between BDE-209 and DBDPE predicates the use of [(13)C(14)]-decabromodiphenylethane as a surrogate standard to improve the accuracy when determining the levels of DBDPE in environmental samples.

Time-resolved generation of a membrane potential by ba3 cytochrome c oxidase from Thermus thermophilus. Evidence for reduction-induced opening of the binuclear center

ba3-type cytochrome c oxidase purified from the thermophilic bacterium Thermus thermophilus has been reconstituted in phospholipid vesicles and laser flash-induced generation of a membrane potential by the enzyme has been studied in a microsecond/ms time scale with Ru(II)-tris-bipyridyl complex (RuBpy) as a photoreductant. Flash-induced single electron reduction of the aerobically oxidized ba3 by RuBpy results in two phases of membrane potential generation by the enzyme with tau values of about 20 and 300 microseconds at pH 8 and 23 degrees C. Spectrophotometric experiments show that oxidized ba3 reacts very poorly with hydrogen peroxide or any of the other exogenous heme iron ligands studied like cyanide, sulfide and azide. At the same time, photoreduction of the enzyme by RuBpy triggers the electrogenic reaction with H2O2 with a second order rate constant of approximately 2 x 10(3) M-1 s-1. The data indicate that single electron reduction of ba3 oxidase opens the binuclear center of the enzyme for exogenous ligands. The fractional contribution of the protonic electrogenic phases induced by peroxide in cytochrome ba3 is much less than in bovine oxidase, pointing to a possibility of a different electrogenic mechanism of the ba3 oxidase as compared to the oxidases of the aa3-type.

Specific cation binding site in mammalian cytochrome oxidase

Calcium ion binds reversibly with cytochrome c oxidase from beef heart mitochondria (Kd approximately 2 microM) shifting alpha- and gamma-absorption bands of heme a to the red. Two sodium ions compete with one Ca2+ for the binding site with an average dissociation constant square root[K1(Na) x K2(Na)] approximately 3.6 mM. The Ca2+-induced spectral shift of heme a is specific for mammalian cytochrome c oxidase and is not observed in bacterial or yeast aa3 oxidases although the Ca2+-binding site has been revealed in the bacterial enzyme [Ostermeier, C., Harrenga, A., Ermler, U. and Michel, H. (1997) Proc. Natl. Acad. Sci. USA 94, 10547-10553]. As His-59 and Gln-63 involved in Ca2+ binding with Subunit I of P. denitrificans oxidase are not conserved in bovine oxidase, these residues have to be substituted by alternative ligands in mammalian enzyme, which is indeed the case as shown by refined structure of bovine heart cytochrome oxidase (S. Yoshikawa, personal communication). We propose that it is interaction of Ca2+ with the species-specific ligand(s) in bovine oxidase that accounts for perturbation of heme a. The Ca2+/Na2+-binding site may be functionally associated with the exit part of 'pore B' proton channel in subunit I of mammalian cytochrome c oxidase.

Effect of pH on the spectrum of cytochrome c oxidase hydrogen peroxide complex

Hydrogen peroxide binding to ferric cytochrome c oxidase in proteoliposomes brings about a red-shift of the enzyme Soret band and increased absorption in the visible range with two prominent peaks at approx. 570 and 607 nm. The molar absorptivity of the H2O2-induced difference spectrum is virtually pH-independent in the Soret band and at 570 nm, whereas the peak at 607 nm increases approx. 3-fold upon alkalinization in a narrow pH range 6.0-7.2, the effect being reversible. The pH profile of this transition indicates ionization of two acid-base groups with close pK values of 6.7. The lineshape of the peroxide compound difference spectrum is found to respond to pH changes inside the proteoliposomes. It is suggested that peroxide-complexed enzyme can undergo a pH-dependent transition to a form with increased extinction at 605-607 nm, possibly corresponding to the 420 nm (or 'pulsed') conformer of the ferric cytochrome oxidase formed as an early product of the enzyme oxidation. Accordingly, relaxation of the '420 nm' form to the resting state would be linked to an uptake of two protons from the M-aqueous phase. This protolytic reaction might be a partial step of the cytochrome oxidase proton pumping mechanism or it could serve to regulate interconversion between the active 'pulsed' and less active 'resting' states of the enzyme in the membrane.

Spectral shifts of cytochrome c oxidase induced by complexons

Ca2+-chelating agents, such as EDTA and ATP, are shown to bring about a rapid spectral response of the oxidized cytochrome c oxidase due to reversal of the Ca2+-induced red shift of the gamma- and alpha-absorption bands of the ferric enzyme. In addition, complexons are found to bring about Ca2+-independent, slow irreversible spectral changes indicative of a conformational transition of cytochrome oxidase. 1 mol EDTA per mol enzyme is sufficient to produce the maximal effect even in the presence of excess Ca2+, indicating high specificity of interaction. It is suggested that the conformation of cytochrome c oxidase may be regulated by the tightly bound "non-redox' metal ions (Mg, Zn, Cux) known to be present in the enzyme. These ions might be involved in specific binding of physiological effectors with chelating properties, such as ATP.

Electrogenic proton exchange between cytochrome a3 active center and M-aqueous phase. Evidence for cytochrome a3-associated input proton well

The rate of cyanide binding with the oxidized cytochrome-c oxidase in proteoliposomes is controlled by ionization of a protein group with pK approximately 6.7, the ligand reacting with the protonated enzyme only [(1983) Bioorg. Chem. (USSR) 9, 216-227]. As shown here, the kinetics of cyanide binding depends on the pH inside the proteoliposomes. The reaction rate is affected by the electrical potential difference across the proteoliposome membranes as if the a3-linked ionizable group exchanged H+ with the proteoliposome interior electrogenically. The data corroborate a hypothesis on the existence of a proton well communicating cytochrome oxidase O2-reducing center with the M-aqueous phase.

Cytochrome b reduction by hexaammineruthenium in mitochondria and submitochondrial particles. Evidence for heme b-562 localization at the M-side of the mitochondrial membrane

In the presence of ascorbate, hexaamineruthenium mediates rapid reduction of cytochrome b-562 in submitochondrial particles but not in mitochondria. The reaction is observed in the combined presence of antimycin (or funiculosin) and myxothiazol, which implies direct interaction of Ru(NH3)2+6 with b cytochrome(s). We assume that contrary to previous conclusions (Case and Leigh (1976) Biochem. J., 160, 769-783) redox centre of at least one of the oxidized cytochromes b, most probably of b-562, is exposed to the M-aqueous phase.

Localization of a ferricyanide-reactive site of cytochrome b-c1 complex, possibly of cytochrome b or ubisemiquinone, at the outer face of submitochondrial particles

When succinate oxidation by submitochondrial particles is blocked by antimycin, NoHOQnO or funiculosin, addition of ferricyanide restores oxygen uptake coupled to membrane potential generation. The effect of ferricyanide is abolished by mucidin or myxothiazol, as well as by KCN. The data strongly favor a cyclic redox loop mechanism in site 2 and show that either heme of the ferrous cytochrome b or ubisemiquinone formed in the QH2-oxidizing center of complex b-c1 is accessible to ferricyanide at the outer (M) side of the submitochondrial particle membrane.