Einarsdóttir O, Georgiadis K E, Dawes T D
Department of Chemistry, University of California, Santa Cruz 95064.
Biochem Biophys Res Commun. 1992 Apr 30;184(2):1035-41. doi: 10.1016/0006-291x(92)90695-h.
Ground state near-infrared absorption spectra of fully reduced unliganded and fully reduced CO (a2+ CuA+ a3(2+)-CO CuB+) cytochrome c oxidase were investigated. Flash-photolysis time-resolved absorption difference spectra of the mixed-valence (a3+ CuA2+ a3(2+)-CO CuB+) and the fully reduced CO complexes were also studied. A band near 785 nm (epsilon approximately 50 M-1cm-1) was observed in the fully reduced unliganded enzyme and the CO photoproducts. The time-resolved 785 nm band disappeared on the same timescale (t1/2 approximately 7 ms) as CO recombined with cytochrome a3(2+). This band, which is attributed to the unliganded five coordinate ferrous cytochrome a3(2+), has some characteristics of band III in deoxy-hemoglobin and deoxy-myoglobin. A second band was observed at approximately 710 nm (epsilon approximately 80 M-1cm-1) in the fully reduced unliganded and the fully reduced CO complexes. This band, which we assign to the low spin ferrous cytochrome a, appears to be affected by the ligation state at the cytochrome a3(2+) site.
研究了完全还原的无配体和完全还原的CO（a2+ CuA+ a3(2+)-CO CuB+）细胞色素c氧化酶的基态近红外吸收光谱。还研究了混合价态（a3+ CuA2+ a3(2+)-CO CuB+）和完全还原的CO复合物的闪光光解时间分辨吸收差光谱。在完全还原的无配体酶和CO光产物中观察到一个接近785 nm的波段（ε约为50 M-1cm-1）。当CO与细胞色素a3(2+)重新结合时，时间分辨的785 nm波段在相同的时间尺度（t1/2约为7 ms）上消失。这个波段归因于无配体的五配位亚铁细胞色素a3(2+)，具有脱氧血红蛋白和脱氧肌红蛋白中带III的一些特征。在完全还原的无配体和完全还原的CO复合物中，在约710 nm处观察到第二个波段（ε约为80 M-1cm-1）。我们将这个波段归因于低自旋亚铁细胞色素a，它似乎受到细胞色素a3(2+)位点的配体状态的影响。
