Das T K, Gomes C M, Teixeira M, Rousseau D L
Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Proc Natl Acad Sci U S A. 1999 Aug 17;96(17):9591-6. doi: 10.1073/pnas.96.17.9591.
The hyperthermophilic archaeon Acidianus ambivalens expresses a membrane-bound aa(3)-type quinol oxidase, when grown aerobically, that we have studied by resonance Raman spectroscopy. The purified aa(3) oxidase, which does not contain bound quinol, undergoes a reversible slow conformational change at heme a(3) upon reduction, as indicated by a change in the frequency of its heme formyl stretching mode, from 1,660 cm(-1) to 1,667 cm(-1). In contrast, upon reduction of the integral membrane enzyme or the purified enzyme preincubated with decylubiquinol, this mode appears at 1,667 cm(-1) much more rapidly, suggesting a role of the bound quinol in controlling the redox-linked conformational changes. The shift of the formyl mode to higher frequency is attributed to a loss of hydrogen bonding that is associated with a group having a pKa of approximately 3.8. Based on these observations, a crucial element for proton translocation involving a redox-linked conformational change near the heme a(3) formyl group is postulated.
嗜热古菌嗜酸两面菌（Acidianus ambivalens）在需氧生长时会表达一种膜结合的aa(3)型喹啉氧化酶，我们已通过共振拉曼光谱对其进行了研究。纯化后的aa(3)氧化酶不含有结合态喹啉，在还原时，其血红素a(3)会发生可逆的缓慢构象变化，这可通过其血红素甲酰基伸缩振动模式的频率变化来表明，该频率从1660厘米-1变为1667厘米-1。相比之下，对于完整膜酶或与癸基泛醌预孵育的纯化酶进行还原时，该模式在1667厘米-1处出现得更快，这表明结合态喹啉在控制氧化还原相关构象变化中发挥作用。甲酰基模式向更高频率的转变归因于与pKa约为3.8的基团相关的氢键的丧失。基于这些观察结果，推测了涉及血红素a(3)甲酰基附近氧化还原相关构象变化的质子转运的关键要素。
