Crystal structure of a laccase from the fungus Trametes versicolor at 1.90-Å resolution containing a full complement of coppers
Crystal structure of a laccase from the fungus Trametes versicolor at 1.90-Å resolution containing a full complement of coppers
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DOI：
10.1074/jbc.m204571200
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发表时间：
2002-10-04
影响因子：
4.8
通讯作者：
Choinowski, T
中科院分区：
文献类型：
--
作者：
Piontek, K;Antorini, M;Choinowski, T
漆酶是一种多酚氧化酶，属于蓝色多铜氧化酶家族。这些酶催化四个还原底物分子的单电子氧化，伴随着分子氧的四电子还原为水。漆酶氧化广泛的底物，优选酚类化合物。在介质的存在下，真菌漆酶表现出扩大的底物范围，然后能够氧化具有超过其自身的氧化还原电位的化合物。到目前为止，只有一个晶体结构的漆酶在一个不活跃的，2型铜耗尽的形式已被报道。我们在这里提出的第一个晶体结构的活性漆酶含有完整的补充铜，完整的多肽链连同七个碳水化合物部分。尽管在新结构中存在所有铜，但两种漆酶的折叠非常相似。然而，第三类铜的协调是明显不同的。在Trametes versicolor漆酶中的三核铜簇的几何形状类似于在抗坏血酸氧化酶和哺乳动物血浆铜蓝蛋白结构中发现的几何形状，这表明铜氧化和O-2还原的共同反应机制。与大多数蓝铜蛋白不同，T.变色漆酶没有轴向配体，并且仅3重配位。以前，氧化还原电位的适度升高归因于缺乏轴向配体。基于目前的结构数据和序列比较，提出了一种机制来解释漆酶如何可以调整其氧化还原电位高达200 MV。
Laccase is a polyphenol oxidase, which belongs to the family of blue multicopper oxidases. These enzymes catalyze the one-electron oxidation of four reducing-substrate molecules concomitant with the four-electron reduction of molecular oxygen to water. Laccases oxidize a broad range of substrates, preferably phenolic compounds. In the presence of mediators, fungal laccases exhibit an enlarged substrate range and are then able to oxidize compounds with a redox potential exceeding their own. Until now, only one crystal structure of a laccase in an inactive, type-2 copper-depleted form has been reported. We present here the first crystal structure of an active laccase containing a full complement of coppers, the complete polypeptide chain together with seven carbohydrate moieties. Despite the presence of all coppers in the new structure, the folds of the two laccases are quite similar. The coordination of the type-3 coppers, however, is distinctly different. The geometry of the trinuclear copper cluster in the Trametes versicolor laccase is similar to that found in the ascorbate oxidase and that of mammalian ceruloplasmin structures, suggesting a common reaction mechanism for the copper oxidation and the O-2 reduction. In contrast to most blue copper proteins, the type-1 copper in the T. versicolor laccase has no axial ligand and is only 3-fold coordinated. Previously, a modest elevation of the redox potential was attributed to the lack of an axial ligand. Based on the present structural data and sequence comparisons, a mechanism is presented to explain how laccases could tune their redox potential by as much as 200 MV.