STRUCTURE OF A UNIQUE TWOFOLD SYMMETRICAL HEME-BINDING SITE
STRUCTURE OF A UNIQUE TWOFOLD SYMMETRICAL HEME-BINDING SITE
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DOI：
10.1038/nsb0794-453
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发表时间：
1994-07-01
期刊：
影响因子：
--
通讯作者：
YARIV, J
中科院分区：
文献类型：
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作者：
FROLOW, F;KALB, AJ;YARIV, J
大肠杆菌的细菌铁蛋白，也称为细胞色素B（1），是由24个相同的蛋白质亚基和12个血红素组成的中空、近球形的外壳。我们已经在2.9埃分辨率下以四氢呋喃晶体形式解决了该结构。我们发现，每个血红素是绑定在一个口袋中形成的一对hemony相关的亚基之间的接口。血红素的准二重轴与这些亚基相关的局部二重轴紧密对齐。血红素的轴向配体具有来自与血红素相关的亚基的两个等同的甲硫氨酰残基（Met 52）的硫。四个水分子的簇被捕获在血红素的上边缘和两个延伸的蛋白质环之间的差距中，所述蛋白质环将血红素与外部水性环境封闭。这是双甲硫氨酸连接血红素结合位点的第一种结构，也是双重对称血红素结合位点的第一种情况。
Bacterioferritin of Escherichia coli, also known as cytochrome b(1), is a hollow, nearly spherical shell made up of 24 identical protein subunits and 12 haems. We have solved this structure in a tetragonal crystal form at 2.9 Angstrom resolution. We find that each haem is bound in a pocket formed by the interface between a pair of symmetry-related subunits. The quasi-twofold axis of the haem is closely aligned with the local twofold axis relating these subunits. The axial ligands of the haem ave sulphurs of two equivalent methionyl residues (Met 52) from the symmetry-related subunits. A cluster of four water molecules is trapped in the gap between the upper edge of the haem and two extended protein loops which close off the haem from the outer aqueous environment. This is the first structure of a bis-methionine ligated haem-binding site and the first case of a twofold symmetric haem-binding site.