摘要
本文分别从不同的植物中分离出豆根瘤血红蛋白,对这些不同来源的豆根瘤血红蛋白的结构以及免疫化学性能进行了比较研究。取得豆根瘤血红蛋白的植物是:三种不同栽培品种的大豆,三种不同栽培品种的三叶草、蛇豆、蚕豆、白羽扇豆以及serradella等共十种植物。检验过的性质包括:免疫化学交叉反应、吸收、热能差异,偏光圆二色性光谱以及这些光谱的配体粘合效应等。这篇报告里还提出了两种新的大豆的豆根瘤血红蛋白的氨基酸序列。 这些豆根瘤血红蛋白都具有比较稳定的。螺旋成份而且含量很高(60-70%),这表明这些豆根瘤血红蛋白的整个分子是摺叠的。这些摺叠的分子性状,不但彼此类似,而且与较高级的肌红蛋白与血红蛋白相一致。可是,血红素部分,在豆根瘤血红蛋白中的位置却与较高级的肌红蛋白不相同,在肌红蛋白这一类较高级的高分子化合物里,血红素是紧密地与蛋白质“口袋”联系在一起的,这种“口袋”是比较容易吸水的;而豆根瘤血红蛋白中的血红素与其蛋白质“口袋”的联系就不那么紧密。两者间的这种差异,就可能说明豆根瘤血红蛋白所具不寻常的配体粘合性能,包括它的高度氧亲合力。 在从同一株植物体内所分离出来的各组豆根瘤血红蛋白或从同一种的不同栽培品种植物所分离出来的各组豆根瘤血红蛋白间,存在着完全的免疫交叉反应;而从不同种植物分离出来的豆根瘤血红蛋白间,则表现相当大的差异。用对比的放射免疫测定技术所测得的数量结果,使我们能够将具有代表性的各种豆根瘤血红蛋白彼此间的系统发育关系确定下来。在种内与种间运用免疫交又反应,使我们能够取得如此细深入的结果:即在豆科植物的进化过程中,种内与种间豆根瘤血红蛋白差异的实质,是基于蛋白质分子中所大量出现的氨基酸替换。
Leghacmoglobins have been isolated from various plant sources and compared with respet to their sturctural and immunochemical properties. The sources were soybean (three cuitivars),trifolium (three cuitivars) , trifolium (three cultivars), snake bean, broad bean, lupin and serradella. The properties examined included immunochemical cross-reactivity, absorption, thermal difference and circular dichroism spectra and the effects of ligand binding on these spectra. Tentative amino acid sequences for two new soybean leghaemoglobins are reported. Their consistently high a-helix contents (60-70%) suggest an overall molecular folding for the leghaemoglobins which is similar in all cases and like that of the higher myoglobins and haemoglobins. The haem moiety, however, is oriented in a different manner to the higher myoglobins, is less lightly associated with the protein "pocket" and the pocket is more accessible to water these differences would explain some of the unusual ligand-binding properties including the high oxygen affinity of the leghaemoglobins. There is complete immuno-cross-reactivity within groups of leghaemoglobins isolated from the same plant and between cultivars (species) of a tribe. The cross-reactivity between tribes varies considerably, and quantitative measurements by a competitive radioimmunoassay technique have enabled us to place the representatives examined, in phylogenetic relationship to each other. The unexpected extent to which cross-reactivity is attenuated within and between species and tribes, is explicable in terms of the extensive amino acid replacements which have occurred during the evolution of leguminosae.
作者
里琦
胡越
李珂纳
塞伯恩
S.J.LEACH;J.G.R.HURRELL;N.A.NICOLA;K.R.THULBORN(Russell Grimwade School of Biochemistry,University of Melbourne,Parkville Victoria 3052 Australia;Biochenistry Restarch Division,Commonwealth Serum Laboratories,Parkvillt,victoria 3052,Australia;Walter nd Eliza Hall Institute of Medical Research,Parkille,Victoria 3052,Australia;Department of Bioclhemistry,Oxford University,South Parks Road,Oxford OXI 2ID,Engfand)