Piatigorsky J
J Biol Chem. 1976 Jul 25;251(14):4416-20.
The predominant protein in the embryonic chick lens, delta-crystallin, is composed of four subunits with molecular weights near 50,000. The degree to which these 4 polypeptides are the same or dissimilar was explored in delta crystallin purified from 15-day-old embryonic chick lenses by relating the numbers of methionine-containing tryptic peptides and cyanogen bromide (CNBr) peptides derived from the native protein to the average number of methionine residues per subunit. Amino acid analyses indicated that 1 mol of native delta-crystallin contains approximately 32 methionine residues, leading to an average of 8 methionine residues per subunit. Approximately equal amounts of 8 methionine-containing tryptic peptides were resolved by two-dimensional thin layer separation on cellulose sheets and by isoelectric focusing in polyacrylamide gels. Nine CNBr peptides were resolved by a combination of electrophoresis in sodium dodecyl sulfate (SDS)-polyacrylamide gels and chromatography on SDS-hydroxylapatite columns. The additive molecular weight of the 9 CNBr peptides was very close to the delta-crystallin subunit molecular weight of 50,000. Thus, the subunits of 15-day-old embryonic chick delta-crystallin have similar sequence of encoded amino acids.
胚胎期鸡晶状体中的主要蛋白质——δ-晶状体蛋白，由四个分子量接近50,000的亚基组成。通过将从15日龄胚胎期鸡晶状体中纯化得到的δ-晶状体蛋白的含甲硫氨酸胰蛋白酶肽和溴化氰（CNBr）肽的数量与每个亚基中甲硫氨酸残基的平均数量相关联，来探究这4种多肽的相同或不同程度。氨基酸分析表明，1摩尔天然δ-晶状体蛋白含有约32个甲硫氨酸残基，即每个亚基平均有8个甲硫氨酸残基。通过在纤维素薄板上进行二维薄层分离以及在聚丙烯酰胺凝胶中进行等电聚焦，分离出了数量大致相等的8种含甲硫氨酸胰蛋白酶肽。通过在十二烷基硫酸钠（SDS）-聚丙烯酰胺凝胶中电泳以及在SDS-羟基磷灰石柱上进行色谱分析相结合的方法，分离出了9种CNBr肽。这9种CNBr肽的相加分子量非常接近50,000的δ-晶状体蛋白亚基分子量。因此，15日龄胚胎期鸡δ-晶状体蛋白的亚基具有相似的编码氨基酸序列。
