Capra J D, Wasserman R L, Kehoe J M
J Exp Med. 1973 Aug 1;138(2):410-27. doi: 10.1084/jem.138.2.410.
Immunoglobulin heavy chains from IgG pools of several mammalian species have been subjected to Edman degradation on an automated protein sequencer. The percentage of unblocked vs. blocked heavy chains was estimated from the yield of the invariant valine in the second position. Further analysis of these unblocked polypeptides unequivocally placed them in the V(HIII) subgroup on the basis of homology with known human heavy chain sequences. The mammals studied could be divided into three distinct categories on the basis of the distribution of the V(HIII) subgroup. In several species the V(HIII) subgroup could not be detected while, in others, virtually all of the heavy chains belonged to this subgroup. Several species had intermediate amounts with the level of the V(HIII) subgroup restricted to between 19 and 29% of the total pool. Within experimental error, all members of a given order had a similar V(HIII) subgroup distribution. Further amino acid sequence studies illustrated a high degree of structural homogeneity in the heavy chains of IgG isolated from pooled sera of a number of mammalian species. The very close amino acid sequence homologies of the amino terminal 24 residues of the various pools corroborated conclusions previously obtained using several myeloma proteins from some of these same species. In particular, certain phylogenetically associated residues were identifiable at characteristic positions in the pools in confirmation of their identification in the myeloma proteins. The simplest assumptions would suggest that these findings are more compatible with a pauci-gene than a multi-gene basis for the generation of antibody diversity.
几种哺乳动物IgG库中的免疫球蛋白重链已在自动蛋白质测序仪上进行了埃德曼降解。根据第二个位置不变缬氨酸的产量估算未封闭重链与封闭重链的百分比。基于与已知人类重链序列的同源性，对这些未封闭多肽的进一步分析明确将它们归为V(HIII)亚组。根据V(HIII)亚组的分布，所研究的哺乳动物可分为三个不同类别。在一些物种中无法检测到V(HIII)亚组，而在其他物种中，几乎所有重链都属于该亚组。有几个物种的含量处于中间水平，V(HIII)亚组的水平限制在总库的19%至29%之间。在实验误差范围内，给定目内的所有成员都有相似的V(HIII)亚组分布。进一步的氨基酸序列研究表明，从多种哺乳动物混合血清中分离出的IgG重链具有高度的结构同质性。各种库中氨基末端24个残基的氨基酸序列高度同源，证实了先前使用来自其中一些相同物种的几种骨髓瘤蛋白得出的结论。特别是，在库中的特征位置可识别某些系统发育相关的残基，从而证实了它们在骨髓瘤蛋白中的识别。最简单的假设表明，这些发现与抗体多样性产生的少基因基础比多基因基础更相符。
