Brostoff S, Eylar E H
Proc Natl Acad Sci U S A. 1971 Apr;68(4):765-9. doi: 10.1073/pnas.68.4.765.
Methylated arginine residues are found at only one site (position 107) of the polypeptide chain of the A1 protein, as shown by analysis of tryptic and peptic peptides; these analyses show 0.2 mole of N(G)-dimethylarginine and 0.4-0.8 mole of N(G)-monomethylarginine per mole of A1 protein. The methylated arginine residues appeared to be relatively resistant to tryptic attack. Both methylated derivatives were isolated from an enzymatic digest of the A1 protein; they were identified by chromatography, electrophoresis, and degradation to citrulline, methylamine, and ornithine on alkaline hydrolysis. The phylogenetic importance of the methylated derivatives was shown by their presence in the human, monkey, bovine, rabbit, guinea pig, rat, chicken, and turtle A1 proteins at the analogous position to that of the bovine sequence: [Formula: see text] We postulate that the methylated arginine residues may serve an important role in the myelin membrane in situ by stabilization of a double-chain structure for the A1 protein; such a double-chain conformation is induced by a (proline)(3) sequence located nearby.
经胰蛋白酶和胃蛋白酶肽段分析表明，甲基化精氨酸残基仅存在于A1蛋白多肽链的一个位点（第107位）；这些分析显示，每摩尔A1蛋白含有0.2摩尔的N(G)-二甲基精氨酸和0.4 - 0.8摩尔的N(G)-单甲基精氨酸。甲基化精氨酸残基似乎对胰蛋白酶的攻击具有相对抗性。两种甲基化衍生物均从A1蛋白的酶解产物中分离得到；通过色谱法、电泳法以及在碱性水解条件下降解为瓜氨酸、甲胺和鸟氨酸对其进行鉴定。甲基化衍生物在系统发育上的重要性体现在它们存在于人类、猴子、牛、兔子、豚鼠、大鼠、鸡和乌龟的A1蛋白中，且位于与牛序列类似的位置：[公式：见正文] 我们推测，甲基化精氨酸残基可能通过稳定A1蛋白的双链结构，在髓鞘膜原位发挥重要作用；这种双链构象是由附近的一个（脯氨酸）(3)序列诱导产生的。
