Department of Biological Science, Graduate School of Science, Shizuoka University, 836 Oh-ya, Suruga-ku, Shizuoka 422–8529, Japan.
Microbes Environ. 2010;25(2):95-102. doi: 10.1264/jsme2.me09154.
Tetraheme cytochrome c-554 is a physiological electron acceptor of hydroxylamine oxidoreductase (HAO), a core enzyme of ammonia oxidation in chemoautotrophic nitrifiers. Here we report the purification of cytochrome c-554 from Nitrosococcus oceani strain NS58, a marine gammaproteobacterial ammonia-oxidizing bacterium. The NS58 cytochrome is a 25 kDa-protein having four hemes c. The absorption spectrum of the cytochrome showed peaks at 420 nm, 523 nm, and 554 nm, with shoulders at around 430 nm and 580 nm in the reduced state. In contrast to the highly basic counterpart from the betaproteobacterium Nitrosomonas europaea, the NS58 cytochrome c-554 was an acidic protein whose isoelectric point was 4.6. HAO was also purified, and the reaction with the NS58 cytochrome was found to be salt-tolerant. Compared with the activity observed in a non-salt solution, 60% of the activity remained in a saline concentration comparable to that of seawater.
四联体细胞色素 c-554 是羟胺氧化还原酶 (HAO) 的一种生理电子受体，后者是化能自养硝化菌中氨氧化的核心酶。本文报道了从海洋γ变形菌氨氧化细菌 Nitrosococcus oceani 株 NS58 中纯化细胞色素 c-554 的方法。该 NS58 细胞色素是一种 25 kDa 的蛋白，具有四个 c 型血红素。细胞色素的吸收光谱在还原状态下于 420nm、523nm 和 554nm 处显示出峰值，在 430nm 和 580nm 处有肩峰。与来自β变形菌 Nitrosomonas europaea 的高度碱性对应物不同，NS58 细胞色素 c-554 是一种酸性蛋白，等电点为 4.6。HAO 也被纯化，并且发现与 NS58 细胞色素的反应具有耐盐性。与在非盐溶液中观察到的活性相比，在类似于海水的盐浓度下，有 60%的活性得以保留。
