鸟类血红蛋白的四级结构和残基选择性特征

QUARTERNARY STRUCTURE FEATURES AND RESIDUE SELECTIVITYOF AVES HEMOGLOBINS

对目前已知结构的三个鸟类血红蛋白与哺乳类和硬骨鱼类血红蛋白的晶体结构数据进行了比较 ,发现鸟类、硬骨鱼类和哺乳类血红蛋白具有不同的四级结构特征 ,鸟类和硬骨鱼类血红蛋白的各亚基间的距离比哺乳类血红蛋白大 ,其中 ,α1 - β1亚基间的距离为 :硬骨鱼类Hb>鸟类Hb>哺乳类Hb ;α1 - β2、α1 -α2和β1 - β2亚基间的距离以及两个αβ 二聚体的距离为 :鸟类Hb>硬骨鱼类Hb>哺乳类Hb。进一步由一级结构的比较发现 ,鸟类、硬骨鱼类和哺乳类血红蛋白具有不同的残基选择性。鸟类和硬骨鱼类血红蛋白倾向于选择侧链更大的残基 ,这些大侧链残基主要分布于分子表面和亚基之间的界面 ,导致四级结构的差异。三类血红蛋白四级结构的微妙差异与它们的协同效应中有机磷效应物的分子大小和形状不同有关 ,鸟类、硬骨鱼类和哺乳类血红蛋白似乎在进化过程中选择了不同大小的残基而进化形成稍有不同的四级结构 ,从而适应与不同的有机磷化合物相结合。

The crystal structures of three aves hemoglobins known hitherto were compared with mammal and teleost hemoglobins. Different quarternary structure features were found for the three vertebrate hemoglobin classes. The distances between subunits of aves and teleost hemoglobins are longer than those of mammal hemoglobins. Concretely, the distances between α1 and β1 subunits are in order: teleost Hb>aves Hb>mammal Hb; the distances between α1 and β2, α1 and α2, β1 and β2, and two αβ dimers are in order: aves Hb>teleost Hb>mammal Hb. Furthermore, sequence comparison showed that aves, teleost and mammal hemoglobins have different residue selectivity. Aves and teleost hemoglobins tend to select residues with larger side chains. These larger residues locate mainly at the molecular surface and subunit interfaces, leading to some differences in the quarternary structures of the three vertebrate Hb classes, which are related to the difference of their organic phosphate effectors. It seems that aves, teleost and mammal hemoglobins select different residues in size in their evolutionary course forming different quarternary structures to adapt the binding of different organic phosphate effectors.