Crystal structure of a functional unit from Octopus hemocyanin
Crystal structure of a functional unit from Octopus hemocyanin
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DOI：
10.1006/jmbi.1998.1647
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发表时间：
1998-05-15
影响因子：
5.6
通讯作者：
Hendrickson, WA
中科院分区：
文献类型：
--
作者：
Cuff, ME;Miller, KI;Hendrickson, WA
血青素是在许多节肢动物和软体动物中发现的巨大的氧转运蛋白。自由溶解在血淋巴中，它们是多亚基蛋白，含有许多活性位点的拷贝，活性位点是铜原子对，可以可逆地结合氧。章鱼血青素由十个亚基组成，每个亚基包含七个氧结合“功能单位”。羧基末端47 kDa功能单元Odg是一种蛋白水解分离物，可可逆结合氧，同时表现出轻微的玻尔和镁离子效应。在这项工作中，我们提出了2.3埃分辨率下Odg的x射线结构测定和分析。Odg有两个结构域：一个很大程度上是螺旋形的铜结合域，以及一个五股反平行的β -三明治结构，具有在许多病毒中发现的果冻卷拓扑结构。六个组氨酸残基连接铜原子，其中一个参与硫醚桥。结果表明，软体动物和节肢动物的血青素除了在第四系结构上的差异外，还具有明显的第三系褶皱。然而，章鱼和马蹄蟹的血青素比较发现了相似的活性位点，这可能是趋同和发散进化的一个显著例子。(C) 1998学术出版社有限公司
Hemocyanins are giant oxygen transport proteins found in many arthropods and molluscs. Freely dissolved in the hemolymph, they are multisubunit proteins that contain many copies of the active site, a copper atom pair that reversibly binds oxygen. Octopus hemocyanin is composed of ten subunits, each of which contain seven oxygen-binding "functional units". The carboxyl-terminal 47 kDa functional unit, Odg, is a proteolytic isolate that binds oxygen reversibly while exhibiting slight Bohr and magnesium ion effects. Ln this work we present the X-ray structure determination and analysis of Odg at 2.3 Angstrom resolution. Odg has two structural domains: a largely alpha-helical copper binding domain, and a five-stranded anti-parallel beta-sandwich with the jelly roll topology found in many viruses. Six histidine residues ligate the copper atoms, one of which is involved in a thioether bridge. The results show that the hemocyanin from the mollusc and that from the arthropod have distinct tertiary folds in addition to the long recognized differences in their quaternary structures, Nonetheless, a comparison of Octopus and horseshoe crab hemocyanin reveals a similar active site, in a striking example of perhaps both convergent and divergent evolution. (C) 1998 Academic Press Limited.