Bishistidyl heme hexacoordination, a key structural property in Drosophila melanogaster hemoglobin
Bishistidyl heme hexacoordination, a key structural property in Drosophila melanogaster hemoglobin
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DOI：
10.1074/jbc.m503814200
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发表时间：
2005-07-22
影响因子：
4.8
通讯作者：
Bolognesi, M
中科院分区：
文献类型：
--
作者：
de Sanctis, D;Dewilde, S;Bolognesi, M
在低氧环境下生活的昆虫幼虫中，很早就分离出高浓度的血红蛋白。相反，最近在果蝇Drosophila melanogaster中发现了一种单体血红蛋白，它是在幼虫和成虫中都表达的细胞内蛋白。这一发现表明，昆虫的氧气供应可能比以前认为的更复杂，不仅依赖于O-2通过管状气管系统的扩散，而且还依赖于载体介导的运输和储存。本文报道了重组D.黑腹血红蛋白，分辨率为1.20埃。光谱数据显示，该蛋白质显示六配位血红素，其轴向配体是近端和远端His残基。血红素的这种双组氨酸连接对蛋白质局部结构具有相当大的影响。三个蛋白质基质腔，大小相当，但不是在拓扑位置与抹香鲸肌红蛋白，通过蛋白质基质传播，其中一个可以容纳氙原子。此外，D.黑腹鱼血红蛋白在靠近EF铰链的表面口袋处结合一分子3-（环己基氨基）丙磺酸（CAPS）缓冲液。尽管达到了高分辨率，没有序列/结构特征，特别是支持血红素六至五配位过渡所需的双原子配体结合可以被确认。
Hemoglobins at high concentration have been isolated long ago from some insect larvae living in hypoxic environments. Conversely, a monomeric hemoglobin has been discovered recently in the fruit fly Drosophila melanogaster as intracellular protein expressed both in larvae and in the adult fly. Such a finding indicates that the oxygen supply in insects may be more complex than previously thought, relying not only on O-2 diffusion through the tubular tracheal system, but also on carrier-mediated transport and storage. We present here the crystal structure of recombinant D. melanogaster hemoglobin at 1.20 angstrom resolution. Spectroscopic data show that the protein displays a hexacoordinated heme, whose axial ligands are the proximal and distal His residues. Such bis-His ligation of the heme has sizable effects on the protein local structure. Three protein matrix cavities, comparable in size but not in topological locations with those of sperm whale myoglobin, are spread through the protein matrix; one of these can host a xenon atom. Additionally, D. melanogaster hemoglobin binds one molecule of 3-(cyclohexylamino) propanesulfonic acid ( CAPS) buffer at a surface pocket, next to the EF hinge. Despite the high resolution achieved, no sequence/structure features specifically supporting the heme hexa- to pentacoordination transition required for diatomic ligand binding could be recognized.