Pfitzner U, Kirichenko A, Konstantinov A A, Mertens M, Wittershagen A, Kolbesen B O, Steffens G C, Harrenga A, Michel H, Ludwig B
Johann Wolfgang Goethe-Universität, Biozentrum, Institut für Biochemie, Molekulare Genetik, Frankfurt, Germany.
FEBS Lett. 1999 Aug 13;456(3):365-9. doi: 10.1016/s0014-5793(99)00977-1.
Recent structure determinations suggested a new binding site for a non-redox active metal ion in subunit I of cytochrome c oxidase both of mitochondrial and of bacterial origin. We analyzed the relevant metal composition of the bovine and the Paracoccus denitrificans enzyme and of bacterial site-directed mutants in several residues presumably liganding this ion. Unlike the mitochondrial enzyme where a low, substoichiometric content of Ca2+ was found, the bacterial wild-type (WT) oxidase showed a stoichiometry of one Ca per enzyme monomer. Mutants in Asp-477 (in immediate vicinity of this site) were clearly diminished in their Ca content and the isolated mutant enzyme revealed a spectral shift in the heme a visible absorption upon Ca addition, which was reversed by Na ions. This spectral behavior, largely comparable to that of the mitochondrial enzyme, was not observed for the bacterial WT oxidase. Further structure refinement revealed a tightly bound water molecule as an additional Ca2+ ligand.
最近的结构测定表明，线粒体和细菌来源的细胞色素c氧化酶亚基I中存在一个非氧化还原活性金属离子的新结合位点。我们分析了牛和反硝化副球菌酶以及细菌定点突变体在几个可能与该离子配位的残基中的相关金属组成。与线粒体酶中发现的低化学计量比的Ca2+含量不同，细菌野生型（WT）氧化酶显示每个酶单体有一个Ca的化学计量比。Asp-477（该位点附近）的突变体Ca含量明显降低，分离出的突变体酶在添加Ca后血红素a可见吸收光谱发生了位移，而Na离子可使其逆转。这种光谱行为在很大程度上与线粒体酶相似，但细菌WT氧化酶未观察到。进一步的结构优化揭示了一个紧密结合的水分子作为额外的Ca2+配体。
