NICKEL IS REQUIRED FOR THE TRANSFER OF ELECTRONS FROM CARBON-MONOXIDE TO THE IRON SULFUR CENTER(S) OF CARBON-MONOXIDE DEHYDROGENASE FROM RHODOSPIRILLUM-RUBRUM
NICKEL IS REQUIRED FOR THE TRANSFER OF ELECTRONS FROM CARBON-MONOXIDE TO THE IRON SULFUR CENTER(S) OF CARBON-MONOXIDE DEHYDROGENASE FROM RHODOSPIRILLUM-RUBRUM
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DOI：
10.1021/bi00438a010
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发表时间：
1989-06-13
期刊：
影响因子：
2.9
通讯作者：
LUDDEN, PW
中科院分区：
文献类型：
--
作者：
ENSIGN, SA;BONAM, D;LUDDEN, PW
研究了红色红螺菌一氧化碳脱氢酶中镍在CO氧化和电子流动中的作用。氧化的含镍(全息)CO脱氢酶的Fe-S中心在CO暴露1分钟内完全还原。在CO存在下孵育35分钟，氧化的缺镍CO脱氢酶的Fe-S中心没有减少。APO-CO脱氢酶Fe-S中心被连二亚硫酸盐还原。在CO存在下，氰化物抑制的HALO-CO脱氢酶的Fe-S中心不被还原，但被二亚硫酸盐还原。钴(II)、锌(II)和铁(II)处理apo-CO脱氢酶后，这些金属离子(M2+的摩尔浓度分别为0.70、1.2和0.86moL)与蛋白质结合，但不增加比活力。纯化的HALO-CO脱氢酶的镍含量为1.1摩尔/摩尔蛋白质，加入NiCl2后不能被进一步激活，这表明该酶上存在一个催化镍中心。与未经处理的脱辅酶相反，经M2+处理的酶不能被加入NiCl2进一步激活，加入NiCl2后，酶的活性被刺激到全酶水平的50-100倍。当置于CO下时，钴处理的酶的Fe-S中心在35分钟的过程中发生还原，而锌和铁处理的酶保持氧化状态。我们的结论是，镍或镍位置上合适的镍类似物，介导了电子从CO向CO脱氢酶的Fe-S中心的流动。
The role of nickel in CO oxidation and electron flow was investigated in carbon monoxide dehydrogenase from Rhodospirillum rubrum. The Fe-S centers of oxidized, nickel-containing (holo) CO dehydrogenase were completely reduced within 1 min of exposure to CO. The Fe-S centers of oxidized, nickel-deficient (apo) CO dehydrogenase were not reduced during a 35-min incubation in the presence of CO. Apo-CO dehydrogenase Fe-S centers were reduced by dithionite. The Fe-S centers of cyanide-inhibited, holo-CO dehydrogenase were not reduced in the presence of CO but were reduced by dithionite. Treatment of apo-CO dehydrogeanse with cobalt(II), zinc(II), and iron(II) resulted in association of these metal ions (0.70, 1.2, and 0.86 mol of M2+mol, respectively) with the protein but no increase in specific activity. Purified holo-CO dehydrogenase contained 1.1 mol of nickel/mol of protein and could not be further activated upon addition of NiCl2, suggesting the presence of one catalytic nickel site on the enzyme. The M2+-treated enzymes could not be further activated by addition of NiCl2 as opposed to the untreated apoenzyme, whose activity was stimulated 50-100-fold to the level of holoenzyme upon addition of NiCl2. When placed under CO, the FE-S centers of the cobalt-treated enzyme became reduced over a 35-min time course, as opposed to the zinc- and iron-treated enzymes, which remained oxidized. We conclude that nickel, or an appropriate nickel analogue in the nickel site, mediates electron flow from CO to the Fe-S centers of CO dehydrogenase.