Prasad R, Hudson B G, Butkowski R, Hamilton J W, Ebner K E
J Biol Chem. 1979 Nov 10;254(21):10607-14.
Three charge forms of rat alpha-lactalbumin were separated by ion exchange chromatography on DEAE-cellulose. The amino acid composition of each form was similar but they differed in carbohydrate composition. Each form contained a tryptic glycopeptide having a common polypeptide and heteropolysaccharide unit. The tryptic glycopeptide was sequenced and positioned in rat alpha-lactalbumin, which was partially sequenced from residues 1 to 50. The carbohydrate attachment site was at Asn45. Secondary structure calculations predicted that Asn45 is in a beta bend conformation whereas Asn45 in bovine alpha-lactalbumin, a poorly glycosylated protein, is not in a bend conformation.
通过在DEAE - 纤维素上进行离子交换色谱法，分离出了大鼠α-乳白蛋白的三种电荷形式。每种形式的氨基酸组成相似，但碳水化合物组成不同。每种形式都含有一种胰蛋白酶糖肽，其具有共同的多肽和杂多糖单元。对该胰蛋白酶糖肽进行了测序，并定位在大鼠α-乳白蛋白中，该蛋白从第1至50个残基进行了部分测序。碳水化合物连接位点位于Asn45处。二级结构计算预测，Asn45处于β-弯曲构象，而糖基化程度低的牛α-乳白蛋白中的Asn45则不处于弯曲构象。
