FT-IR Characterization of the Light-Induced Ni-L2 and Ni-L3 States of [NiFe] Hydrogenase from Desulfovibrio vulgaris Miyazaki F

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• 作者：Hulin Tai ; Koji Nishikawa ; Seiya Inoue ; Yoshiki Higuchi ; Shun Hirota
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：October 29, 2015
• 年：2015
• 卷：119
• 期：43
• 页码：13668-13674
• 全文大小：405K
• ISSN：1520-5207

文摘

Different light-induced Ni-L states of [NiFe] hydrogenase from its Ni-C state have previously been observed by EPR spectroscopy. Herein, we succeeded in detecting simultaneously two Ni-L states of [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F by FT-IR spectroscopy. A new light-induced 谓_CO band at 1890 cm^鈥? and 谓_CN bands at 2034 and 2047 cm^鈥? were detected in the FT-IR spectra of the H₂-activated enzyme under N₂ atmosphere at basic conditions, in addition to the 1910 cm^鈥? 谓_CO band and 2047 and 2061 cm^鈥? 谓_CN bands of the Ni-L2 state. The new bands were attributed to the Ni-L3 state by comparison of the FT-IR and EPR spectra. The 谓_CO and 谓_CN frequencies of the Ni-L3 state are the lowest frequencies observed among the corresponding frequencies of standard-type [NiFe] hydrogenases in various redox states. These results indicate that a residue, presumably Ni-coordinating Cys546, is protonated and deprotonated in the Ni-L2 and Ni-L3 states, respectively. Relatively small 螖H (6.4 卤 0.8 kJ mol^鈥?) and 螖S (25.5 卤 10.3 J mol^鈥? K^鈥?) values were obtained for the conversion from the Ni-L2 to Ni-L3 state, which was in agreement with the previous proposals that deprotonation of Cys546 is important for the catalytic reaction of the enzyme.