Russell D W, Schneider W J, Yamamoto T, Luskey K L, Brown M S, Goldstein J L
Cell. 1984 Jun;37(2):577-85. doi: 10.1016/0092-8674(84)90388-x.
The nucleotide sequence of a partial cDNA for the bovine low-density lipoprotein (LDL) receptor revealed an open reading frame of 264 amino acids that encodes the COOH-terminal 25% of the receptor protein. The sequence predicts a cytoplasmic domain of 50 amino acids at the COOH terminus, followed in order by a membrane-spanning region of 27 hydrophobic amino acids and an externally disposed stretch of 42 amino acids, that is rich in serine and threonine residues and appears to be the site of O-linked glycosylation. This orientation was confirmed by proteolysis experiments in which the relevant fragments were localized by blotting with anti-peptide antibodies and a galactose-specific lectin. The extracytoplasmic domain of the LDL receptor contains a region that is 38% identical with a 96 amino acid sequence in the precursor to mouse epidermal growth factor (EGF), a peptide hormone. This unexpected homology raises the possibility that proteins involved in growth stimulation (e.g., EGF precursor) and nutrient delivery (e.g., LDL receptor) may have a common evolutionary origin.
牛低密度脂蛋白（LDL）受体部分cDNA的核苷酸序列显示出一个264个氨基酸的开放阅读框，该阅读框编码受体蛋白的羧基末端25%。该序列预测在羧基末端有一个50个氨基酸的胞质结构域，接着依次是一个由27个疏水氨基酸组成的跨膜区域和一段42个氨基酸的胞外延伸区域，该区域富含丝氨酸和苏氨酸残基，似乎是O-连接糖基化的位点。通过蛋白水解实验证实了这种取向，在该实验中，相关片段通过用抗肽抗体和半乳糖特异性凝集素进行印迹定位。LDL受体的胞外结构域包含一个区域，该区域与小鼠表皮生长因子（EGF，一种肽激素）前体中的96个氨基酸序列有38%的同一性。这种意外的同源性增加了参与生长刺激（如EGF前体）和营养物质传递（如LDL受体）的蛋白质可能有共同进化起源的可能性。
