Knauer D J, Wagner F W, Smith G L
School of Life Sciences, University of Nebraska, Lincoln 68583.
J Supramol Struct Cell Biochem. 1981;15(2):177-91. doi: 10.1002/jsscb.1981.380150209.
The rat liver cell line, BRL-3A, is known to produce a family of polypeptides referred to as multiplication-stimulating-activity (MSA). Serum-free conditioned medium from this cell line is a rich source for the purification of these somatomedin-like molecules. Somatomedins in serum, as well as MSA produced by BRL-3A cells in culture, exist primarily as a high molecular weight complex bound to specific carrier proteins. This study describes the purification of the MSA carrier protein (MCP) from conditioned medium using affinity chromatographic procedures. The purified carrier protein is shown to specifically bind labeled MSA and generates a complex with an apparent molecular weight of 60,000-70,000 daltons. Characterization of the carrier protein indicates that it consists of two different noncovalently linked protein chains with apparent molecular weights of 30,000 and 31,500 daltons. The availability of a pure carrier protein should provide a unique opportunity to investigate the functional significance of the carrier protein in the biological activity of the somatomedins.
大鼠肝细胞系BRL-3A已知可产生一类被称为增殖刺激活性（MSA）的多肽。该细胞系的无血清条件培养基是纯化这些类生长调节素分子的丰富来源。血清中的生长调节素以及培养的BRL-3A细胞产生的MSA，主要以与特定载体蛋白结合的高分子量复合物形式存在。本研究描述了使用亲和色谱法从条件培养基中纯化MSA载体蛋白（MCP）的过程。纯化的载体蛋白显示能特异性结合标记的MSA，并形成一种表观分子量为60,000 - 70,000道尔顿的复合物。对载体蛋白的特性分析表明，它由两条不同的非共价连接的蛋白链组成，表观分子量分别为30,000和31,500道尔顿。纯载体蛋白的可得性应为研究载体蛋白在生长调节素生物活性中的功能意义提供一个独特的机会。
