Observation of the equilibrium CuB-CO complex and functional implications of the transient heme a3 propionates in cytochrome ba3-CO from Thermus thermophilus. Fourier transform infrared (FTIR) and time-resolved step-scan FTIR studies.
Observation of the equilibrium CuB-CO complex and functional implications of the transient heme a3 propionates in cytochrome ba3-CO from Thermus thermophilus. Fourier transform infrared (FTIR) and time-resolved step-scan FTIR studies.
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DOI：
10.1074/jbc.m204943200
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发表时间：
2002-09
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影响因子：
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通讯作者：
Konstantinos Koutsoupakis;S. Stavrakis;Eftychia Pinakoulaki;T. Soulimane;C. Varotsis
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文献类型：
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作者：
Konstantinos Koutsoupakis;S. Stavrakis;Eftychia Pinakoulaki;T. Soulimane;C. Varotsis
我们首次报道了在室温下，嗜热嗜热菌中存在CO结合的还原细胞色素ba(3)的铜(B)1+-CO平衡物种的证据。在H(2)O/D(2)O交换和Pd 5.5~9.7之间，Cu(B)1+-CO的C-O伸缩模式的频率在2053 cm(-1)处保持不变，表明化学环境没有改变组氨酸配体的质子化状态。本文报道的数据和结论与最近报道的(Das，T.K.，Tomson，F.K.，Gennis，R.B.，Gordon，M.和Rousseau，D.L.(2001)BiPhys)报道的Cu(B)-His-290的质子化状态的变化相反。J.80,2039-2045和Das，T.P.，Gomees，C.M.，Teixeira，M.和Rousseau，D.L.(1999)Proc.娜塔莉。阿卡德。SCI。美国，96,9591-9596)。时间分辨步进扫描红外光谱表明，瞬时铜(B)1+-CO络合物的衰变速率为34.5 S(-1)，与血红素a(3)发生再结合，k(2)=28.6 S(-1)。瞬时铜(B)~(1+)-CO络合物的衰减速率与吸收在1694(+)/1706(-)处的变化相似，这归因于血红素a(3)丙酸酯(COOH)的微扰。暂态Cu(B)1+-CO物种的Nu(C-O)与平衡状态的Cu(B)1+-CO物种的Nu(C-O)相同，在Pd为5.5-9.7的范围内保持不变，表明在这两种状态之间，Cu(B)没有发生结构变化。讨论了这些结果对血红素-铜氧化酶中质子途径的影响。
We report the first evidence for the existence of the equilibrium Cu(B)1+-CO species of CO-bound reduced cytochrome ba(3) from Thermus thermophilus at room temperature. The frequency of the C-O stretching mode of Cu(B)1+-CO is located at 2053 cm(-1) and remains unchanged in H(2)O/D(2)O exchanges and, between pD 5.5 and 9.7, indicating that the chemical environment does not alter the protonation state of the Cu(B) histidine ligands. The data and conclusions reported here are in contrast to the changes in protonation state of Cu(B)-His-290, reported recently (Das, T. K., Tomson, F. K., Gennis, R. B., Gordon, M., and Rousseau, D. L. (2001) Biophys. J. 80, 2039-2045 and Das, T. P., Gomes, C. M., Teixeira, M., and Rousseau, D. L. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 9591-9596). The time-resolved step-scan FTIR difference spectra indicate that the rate of decay of the transient Cu(B)1+-CO complex is 34.5 s(-1) and rebinding to heme a(3) occurs with k(2) = 28.6 s(-1). The rate of decay of the transient Cu(B)1+-CO complex displays a similar time constant as the absorption changes at 1694(+)/1706(-), attributed to perturbation of the heme a(3) propionates (COOH). The nu(C-O) of the transient Cu(B)1+-CO species is the same as that of the equilibrium Cu(B)1+-CO species and remains unchanged in the pD range 5.5-9.7 indicating that no structural change takes place at Cu(B) between these states. The implications of these results with respect to proton pathways in heme-copper oxidases are discussed.