Cunningham B A, Pflumm M N, Rutishauser U, Edelman G M
Proc Natl Acad Sci U S A. 1969 Nov;64(3):997-1003. doi: 10.1073/pnas.64.3.997.
The amino acid sequence of the first 133 residues of the heavy (gamma) chain from a human gammaG immunoglobulin (He) has been determined. This gamma-chain is identical in Gm type to that of protein Eu, the complete sequence of which has been reported. Comparison of the two sequences substantiates the previous suggestion that there are subgroups of variable regions of heavy chains. The variable region of Eu has been assigned to subgroup I and that of He to subgroup II; on the other hand, the constant regions of the two proteins appear to be identical. Comparison of the sequence of the heavy chain of He with the heavy chain sequences determined in other laboratories suggests that the variable region of subgroup II is at least 118 residues long. The nature and distribution of amino acid variations in this heavy chain subgroup resemble those observed in light chain subgroups. These studies provide evidence that the translocation hypothesis applies to heavy as well as to light chains, viz., genes for variable regions (V) are somatically translocated to genes for constant regions (C) to form complete VC structural genes.
已确定人γG免疫球蛋白（He）重（γ）链前133个残基的氨基酸序列。该γ链在Gm型上与蛋白质Eu的γ链相同，其完整序列已被报道。对这两个序列的比较证实了先前关于重链可变区存在亚组的推测。Eu的可变区已被归入I亚组，He的可变区已被归入II亚组；另一方面，这两种蛋白质的恒定区似乎是相同的。将He重链序列与其他实验室确定的重链序列进行比较表明，II亚组的可变区长至少118个残基。该重链亚组中氨基酸变异的性质和分布类似于轻链亚组中观察到的情况。这些研究提供了证据，表明易位假说是适用于重链以及轻链的，即，可变区（V）基因在体细胞中易位到恒定区（C）基因，以形成完整的VC结构基因。
