Milstein C, Frangione B
Biochem J. 1971 Jan;121(2):217-25. doi: 10.1042/bj1210217.
Amino acid sequences around the disulphide bridges of the heavy chain of an immunoglobulin of the gamma2 subclass have been studied. The protein was digested with pepsin and the digest fractionated by Sephadex. Screening of the eluate by one-dimensional electrophoresis of oxidized and unoxidized samples was used as an assay and pools of fractions were prepared. Identification by diagonal electrophoresis of several inter- and intra-chain disulphide bridges was done on the pooled fractions. The inter-heavy-chain bridged peptide included four cystine residues. Comparison with proteins of other human subclasses indicated that the intrachain bridges identified are the bridges of the invariable section of gamma2 heavy chains. The amino acid sequence of one cysteic acid peptide that may have been derived from the variable part of the molecule was determined. Partial reduction followed by carboxymethylation with radioactive iodoacetate of two proteins of the gamma2 class showed a number of labelled peptides that could be identified as being related to the inter-chain bonded cystine residues.
已对γ2亚类免疫球蛋白重链中二硫键周围的氨基酸序列进行了研究。用胃蛋白酶消化该蛋白质，并通过葡聚糖凝胶对消化产物进行分级分离。通过对氧化和未氧化样品进行一维电泳来筛选洗脱液，并制备各组分的汇集物。对汇集的组分进行对角线电泳，以鉴定几条链间和链内二硫键。重链间桥连肽包含四个半胱氨酸残基。与其他人亚类蛋白质的比较表明，所鉴定的链内桥是γ2重链恒定区的桥。确定了一条可能源自分子可变部分的半胱氨酸肽的氨基酸序列。用放射性碘乙酸对γ2类的两种蛋白质进行部分还原，然后进行羧甲基化，结果显示出许多可鉴定为与链间结合的半胱氨酸残基相关的标记肽。
