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Reaction center chlorophylls (Chls) in photosystems II and I were studied in the isolated thylakoid membranes of a cyanobacterium, Acaryochloris marina, which contains Chls d and a as the major and minor pigments, respectively. The membranes contained PS I and II complexes at a 1.8:1 molar ratio on the basis of the spin densities on the tyrosine D radical(More)
Effects of adding monovalent alkali metal cations to Ca(2+)-depleted photosystem (PS)II membranes on the biochemical and spectroscopic properties of the oxygen-evolving complex were studied. The Ca(2+)-dependent oxygen evolution was competitively inhibited by K(+), Rb(+), and Cs(+), the ionic radii of which are larger than the radius of Ca(2+) but not(More)
Rhodococcus rhodochrous J1 produces high- and low-molecular mass nitrile hydratases (H-NHase and L-NHase, respectively), depending on the inducer. The incorporation of cobalt into L-NHase has been found to depend on the α-subunit exchange between cobalt-free L-NHase (apo-L-NHase) and its cobalt-containing mediator, NhlAE (holo-NhlAE), this novel mode of(More)
Electron transfer in the membranes and the type I reaction center (RC) core protein complex isolated from Heliobacterium modesticaldum was studied by optical and ESR spectroscopy. The RC is a homodimer of PshA proteins. In the isolated membranes, illumination at 14 K led to accumulation of a stable ESR signal of the reduced iron-sulfur center F(B)(-) in the(More)
The function of menaquinone as electron acceptor A 1 was identified by EPR in the purified type 1 homodimeric reaction center core complex (RC core) of an anoxygenic photosynthetic bacterium, Heliobacterium modesticaldum. After illumination of the RC core at 210 K in the absence and presence of dithionite, we detected the radical of a special pair of(More)
Doublet signal and singlet-like signal induced in Ca(2+)-depleted PS II were investigated by pulsed EPR in one-dimensionally oriented photosystem (PS) II membranes. The doublet signal showed marked angular dependent change in its spectrum in term of the applied magnetic field, indicating that the magnetic dipole-dipole interaction is mainly responsible for(More)
A blue-copper protein auracyanin of the filamentous anoxygenic phototroph Roseiflexus castenholzii was purified and characterized. Genomic sequence analysis showed that R. castenholzii has only one auracyanin, whereas Chloroflexus aurantiacus is known to have two auracyanins, A and B. Absorption spectrum of the Roseiflexus auracyanin was similar to that of(More)
Binding of Mn2+ to manganese-depleted photosystem II and electron donation from the bound Mn2+ to an oxidized YZ tyrosine were studied under the same equilibrium conditions. Mn2+ associated with the depleted membranes in a nonsaturating manner when added alone, but only one Mn2+ ion per photosystem II (PS II) was bound to the membranes in the presence of(More)
Photosynthetic O(2) evolution takes place at the Mn cluster in photosystem II (PSII) by oxidation of water. It has been proposed that ammonia, one of water analogues, functions as an inhibitor of O(2) evolution at alkaline pH. However, the detailed mechanism of inhibition has not been understood yet. In this study, we investigated the mechanism of ammonia(More)