Mutagenesis analysis of hydrogen bond network formed in bovine heart cytochrome c oxidase

我们进行了诱变分析的氢键网络，指定为D-途径，形成在牛心脏细胞色素c氧化酶采用HeLa细胞牛/人杂交酶表达系统由我们开发的。在细菌酶中也发现了对应于该D-途径的途径，并且已经提出输送泵送质子和水形成质子。这两种途径的结构几乎彼此相同，并且细菌酶所必需的氨基酸残基在牛酶中是保守的。因此，人们认为这两者具有相同的功能，从而与我们提出的牛酶的质子泵送途径相反。本研究结果有力地表明D-途径不是用于泵质子，而是用于水形成质子。

We carried out mutagenesis analyses of a hydrogen bond network, designated as D-pathway, formed in the bovine heart cytochrome c oxidase employing HeLa cell bovine/human hybrid enzyme expression system developed by us. A pathway corresponding to this D-pathway is also found in the bacterial enzymes, and has been proposed to convey both pumping and water forming protons. The structures of these two pathways are almost identical to each other and amino acid residues essential to the bacterial enzymes are conserved in the bovine enzyme. Hence, it has been thought that these two have the same function, thereby opposing to the proton-pumping pathway of the bovine enzyme proposed by us. The results of this study strongly suggest D-pathway is not for pumping proton but for water forming proton.