Krusius T, Gehlsen K R, Ruoslahti E
Cancer Research Center, La Jolla Cancer Research Foundation, California 92037.
J Biol Chem. 1987 Sep 25;262(27):13120-5.
We have isolated cDNA clones that code for a proteoglycan-related polypeptide with unique properties. A lambda gt11 expression library made from human fibroblast mRNA was screened with an antiserum made against a proteoglycan fraction from human fetal membranes. One group of positive clones revealed an open reading frame coding for 685 amino acids from the COOH terminus of a polypeptide. This amino acid sequence contains a domain that is strongly homologous with the COOH-terminal core protein domain of the large aggregating cartilage proteoglycan. This domain also contains sequences that are homologous with vertebrate lectins that bind terminal galactosyl, N-acetyl-glucosaminyl or mannosyl residues. On the NH2-terminal side of the lectin-like domain the cDNA-derived amino acid sequence contains two epidermal growth factor-related segments. The cDNA clones were shown to belong to a chondroitin sulfate proteoglycan by using antisera made against two peptides predicted from the cDNA sequence. These antisera were reactive with a proteoglycan fraction from fibroblasts after chondroitinase treatment of the fraction but not after treatment with heparinase or no treatment. Among the several polypeptides reactive with the anti-peptide antibodies the largest one, corresponding to a molecular weight of about 400,000, is likely to be the intact core protein, whereas the smaller polypeptides may be processing products or products of artifactual proteolysis. These results show that the amino acid sequence belongs to a proteoglycan core protein, and the sequence, therefore, provides a molecular definition to this proteoglycan. The lectin-related and growth factor-like sequences in the core protein of this proteoglycan suggest that it may play a role in intercellular signaling.
我们已经分离出编码具有独特性质的蛋白聚糖相关多肽的cDNA克隆。用人成纤维细胞mRNA构建的λgt11表达文库，用针对人胎膜蛋白聚糖组分制备的抗血清进行筛选。一组阳性克隆揭示了一个开放阅读框，其编码来自一种多肽COOH末端的685个氨基酸。该氨基酸序列包含一个与大型聚集软骨蛋白聚糖的COOH末端核心蛋白结构域高度同源的结构域。该结构域还包含与结合末端半乳糖基、N-乙酰葡糖胺基或甘露糖基残基的脊椎动物凝集素同源的序列。在凝集素样结构域的NH2末端一侧，cDNA推导的氨基酸序列包含两个表皮生长因子相关片段。通过使用针对从cDNA序列预测的两种肽制备的抗血清，表明这些cDNA克隆属于硫酸软骨素蛋白聚糖。这些抗血清在对该组分进行软骨素酶处理后与成纤维细胞的蛋白聚糖组分发生反应，但在肝素酶处理后或未处理时不发生反应。在与抗肽抗体反应的几种多肽中，最大的一种，分子量约为400,000，可能是完整的核心蛋白，而较小的多肽可能是加工产物或人为蛋白水解产物。这些结果表明该氨基酸序列属于一种蛋白聚糖核心蛋白，因此该序列为这种蛋白聚糖提供了分子定义。这种蛋白聚糖核心蛋白中的凝集素相关和生长因子样序列表明它可能在细胞间信号传导中发挥作用。
