GENE MUTATIONS IN HUMAN HAEMOGLOBIN - CHEMICAL DIFFERENCE BETWEEN NORMAL AND SICKLE CELL HAEMOGLOBIN
GENE MUTATIONS IN HUMAN HAEMOGLOBIN - CHEMICAL DIFFERENCE BETWEEN NORMAL AND SICKLE CELL HAEMOGLOBIN
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DOI：
10.1038/180326a0
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发表时间：
1957-01-01
期刊：
影响因子：
64.8
通讯作者：
INGRAM, VM
中科院分区：
文献类型：
--
作者：
INGRAM, VM
Val-Leu-Leu-Thr-Pro-Glu-Glu-Lys血红蛋白S（虚线）：His-Val-Leu-Leu-Thr-Pro-Val-Glu-Iys也是游离氨基酸，图中省略了。用氟-2，4-二硝基苯法测定了大部分肽的N-末端氨基酸。这些片段与氨基酸组成一起表明了图1所示的血红蛋白A和S的4号肽的序列。唯一不明确的是苏氨酸后面的氨基酸。在此，将来自盐酸裂解的相关产物-苏氨酰-脯氨酰-谷氨酰-赖氨酸和苏氨酰-脯氨酰-缬氨酰-赖氨酸-在纸条上进行两个循环的逐步Edman降解 **。结果表明，在这两种情况下的序列苏氨酰脯氨酰。图1所示的两个4号肽的电荷分布是从两个肽的电泳行为推导出来的，特别是与较小的分裂肽的行为有关。在两种4号肽之间发现的唯一差异是血红蛋白A肽的第一个谷氨酸残基被血红蛋白S肽中的缬氨酸取代。从X射线晶体学和化学研究中得知，分子量为66，700的人血红蛋白分子由两个相同的半分子组成，每个半分子约为33，000。据信，这种发生在两个相同半分子中的取代构成了正常和镰状细胞贫血血红蛋白之间的唯一化学差异。当然，这两种蛋白质的hæm基团是相同的。在每个半分子中，谷氨酸被中性氨基酸缬氨酸取代，这一事实与以前的发现一致，即整个血红蛋白S分子比正常蛋白质"*"少两到三个羧基。胰蛋白酶消化物的所有其他肽在两个"指纹"中占据相同的特征位置。现在已经对这些肽进行了定性氨基酸分析，但未能揭示它们之间的任何差异。因此，它们似乎有可能具有相同的结构，剩下的两个4号肽是唯一不同的肽。大约30%的血红蛋白分子不易受胰蛋白酶的攻击，不会出现在"指纹"上。为了排除在这些大的血红蛋白A和S片段中存在额外差异的可能性，将它们用糜蛋白酶消化，
Val–Leu-Leu-Thr-Pro–Glu-Glu-Lys. Haemoglobin S (broken lines): His–Val–Leu–Leu-Thr-Pro–Val–Glu–Iys also free amino-acids, which are omitted from the figure. The N-terminal amino-acids of most of these peptides were determined by the fluoro-2, 4-dinitrobenzene method". Together with the amino-acid compositions, these fragments indicated the sequences of the No. 4 peptides of hæmoglobins A and S shown in Fig. l. The only ambiguity was the amino-acid following threonine. Here the relevant products from the hydrochloric acid splitting–threonyl-prolylglutamyl-glutamyl-lysine and threonyl-prolyl-valylglutamyl-lysine-were subjected, on paper strips, to a stepwise Edman degradation for two cycles**. The results indicated the sequence threonyl-prolyl-in both cases. The charge distribution of the two No. 4 peptides shown in Fig. 1 was deduced from the electrophoretic behaviour of the two peptides, especially in relation to the behaviour of the smaller split peptides. The only difference found between the two No. 4 peptides is that the first glutamic acid residue of the hæmoglobin A peptide is replaced by valine in the hæmoglobin S peptide. It is known from X-ray crystallographic" and from chemical" studies that the human hæmoglobin molecule of molecular vveight 66,700 is composed of two identical half-molecules, each approximately 33,000. It is believed that this substitution, which occurs in each of the two identical half-molecules, constitutes the only chemical difference between normal and sickle cell anæmia hæmoglobins. Certainly the hæm groups of the two proteins are the same". The fact that in each half-molecule a glutamic acid is replaced by the neutral amino-acid valine agrees with previous findings that the whole hæmoglobin S molecule has two to three carboxyl groups fewer than the normal protein"*". All the other peptides of the tryptic digest occupy identical, and characteristic, positions in the two “finger-prints'. Qualitative amino-acid analyses of these peptides have now been carried out, but have failed to reveal any differences between them. It would seem probable, therefore, that they have identical structures, leaving the two No. 4 peptides as the only ones that differ. About 30 per cent of the hæmoglobin molecule is not susceptible to attack by trypsin and does not appear on the “finger-print”. To eliminate the possibility that an additional difference resides in these large hæmoglobin A and S fragments, they were digested with chymotrypsin, which attacks them