Febs Letters

Ovchinnikov, Yu.A.; Abdulaev, N.G.; Zolotarev, A.S.; Shmukler, B.E.; Zargarov, A.A.; Kutuzov, M.A.; Telezhinskaya, I.N.; Levina, N.B.

doi: 10.1016/0014-5793(88)80739-7pmid: 2834225

The L‐subunit primary structure of the reaction centre from Chloroflexus aurantiacus composed of 310 amino acid residues has been determined by parallel analysis of the protein and corresponding DNA. Significant homology between this protein and L‐subunits from reaction centres of purple bacteria is observed. This implies close similarity in the tertiary structure of these proteins.

Poole, Robert K.; Williams, Huw D.

doi: 10.1016/0014-5793(88)80740-3pmid: 3282921

Reduced minus aerated difference spectra of membranes from Escherichia coli (grown under oxygen‐limited conditions) show, in addition to the 650 nm trough attributed to the oxygenated form of cytochrome d, a smaller trough centred at about 680 nm of unknown origin. When the reference spectrum is that of a sample oxidized with ferricyanide and to which hydrogen peroxide was added, the trough proportions changed, the 680 nm species being more dominant. Similarly, when 8.8 mM hydrogen peroxide is added to a persulphate‐oxidized sample, a peak at 680 nm is immediately formed. No such compound is observed when peroxide is added to persulphate‐oxidized membranes from a cytochrome d‐deficient mutant. It is concluded that the 680 nm species represents a peroxy form of haem d, which is stable at room temperature and is probably an intermediate in the reaction mechanism of this oxidase.

Wikström, Mårten

doi: 10.1016/0014-5793(88)80741-5pmid: 2834226

The oxidised (ferric‐cupric) binuclear centre of cytochrome oxidase is converted into two other states, presumably ferryl‐cupric (F) and ferric‐peroxy‐cupric (P), by energy‐dependent reversed electron transfer from the centre (and water) to cytochrome c [(1981) Proc. Natl. Acad. Sci. USA 78, 4051–4054; (1987) Chem. Scr. 27B, 53–58]. This sequence of events represents a partial reversal of the O2 reduction catalysed by the centre. Here it is shown that the strong pH‐dependence of these reactions is exerted specifically from the matrix (M) side of the inner mitochondrial membrane. This proves un‐equivocally that the binuclear centre generates protonmotive force by means of its vectorial accessibility for electrons and protons.

Raguzzi, Fabio; Lesuisse, Emmanuel; Crichton, Robert R.

doi: 10.1016/0014-5793(88)80742-7pmid: 3282922

A ferritin‐like molecule was purified from iron‐loaded cells of Saccharomyces cerevisiae, but its iron content was very low and was not representative of the cellular iron content. A study of the intracellular distribution of iron has shown that the vacuoles are involved in the storage of iron in the yeast cell. Moreover, it seems that this vacuolar iron can be further utilised by the cells for iron‐requiring processes such as mitochondriogenesis.

Oettmeier, Walter; Masson, Klaus; Donner, Andreas

doi: 10.1016/0014-5793(88)80743-9pmid: N/A

Various substituted 9,10‐anthraquinones were tested for their inhibitory activity on photosystem II electron transport. Maximal inhibitory activity was achieved if the positions adjacent to one of the quinone carbonyl groups were unsubstituted or substituted by hydroxyl groups only. The best anthraquinone type inhibitor found so far was 2,3,4‐trichloro‐1‐hydroxy‐anthraquinone with a pI 50 value of 7.75. This is well comparable to the most powerful known photosystem II inhibitors. As studied by binding experiments with 1‐[14C]methoxy‐anthraquinone, after covalent modification of thylakoids with azido‐atrazine, anthraquinones bind at the photosystem II D1 protein. Their orientation within the binding niche seems to be different from that of other photosystem II inhibitors.

Miyamoto, Yusei; Balkovetz, Daniel F.; Leibach, Frederick H.; Mahesh, Virendra B.; Ganapathy, Vadivel

doi: 10.1016/0014-5793(88)80744-0pmid: 3360130

Uptake of taurine in human placental brush‐border membrane vesicles was greatly stimulated in the presence of an inwardly‐directed Na+ + Cl−‐gradient and uphill transport of taurine could be demonstrated under these conditions. Na+ as well as Cl− were obligatory for this uptake and both ion gradients could energize the uphill transport. This Na+ + Cl−‐gradient‐dependent taurine uptake was stimulated by an inside‐negative membrane potential, demonstrating the electrogenicity of the process. The uptake system was highly specific for β‐amino acids and the K m of the system for taurine was 6.5 ± 0.4 μM.

Malmström, Bo G.

doi: 10.1016/0014-5793(88)80745-2pmid: 2834227

In a Review‐Hypothesis, Mitchell [(1987) FEBS Lett. 222, 235–245] has recently suggested possible molecular mechanisms for proton translocation by cytochrome oxidase. In describing these mechanisms, he extended his own concept of a redox loop in a manner expected to lead to confusion. He also stated that the term redox‐linked proton pump implies an indirect coupling between electron transfer and proton translocation, and that this type of coupling is very difficult to test experimentally. Here it is argued that the original meaning of a redox loop should be maintained, and proper definitions of the terms redox‐linked proton pump and direct or indirect coupling are formulated. In addition, it is reasoned that both types of coupling are amenable to experimental tests.

Mitchell, Peter

doi: 10.1016/0014-5793(88)80746-4pmid: 2834228

In recent papers on protonmotive redox mechanisms in cytochrome oxidase in [(1987) FEBS Lett. 222, 235–245] and [Glynn Biological Research Reports (1987) 3, 1–7], I have suggested that a copper centre may enable the H2O/OH or H2O/O couple to act as the hydrogen‐carrying arm of a redox loop by means of a (CuOH2)+/(CuOH)+ or (CuOH2)+/ (CuO)+ system at the centre. I here explain that critical comments by Malmström [(1988) FEBS Lett. 231, 268–269] on the first of these papers, which might also be levelled at the second, depend on a misunderstanding. I also respond to Malmström's comment about testing conformationally coupled proton‐pump mechanisms.