Lyons R M, Smith G L
Mol Cell Endocrinol. 1986 May;45(2-3):263-70. doi: 10.1016/0303-7207(86)90156-5.
A cloned rat liver cell line (BRL-3A) synthesizes and secretes the somatomedin, Multiplication-Stimulating Activity (MSA), in association with its specific carrier protein (MCP). Affinity-purified MCP is a single-chain polypeptide with a molecular weight of 31,500 under non-reducing conditions and 34,000 when fully reduced. The formation of a Mr 42,000 complex following chemical crosslinking of purified MSA (Mr 8700) and MCP (Mr 34,000) suggests that these components bind in a 1:1 molar ratio on the basis of the sum of their combined molecular weights. The amino acid composition and the N-terminal amino acid sequence of MCP were also determined. Polyclonal MCP-antibody preparations were used to determine if MCP could be detected in normal rat sera. MCP could not be detected in adult rat serum, but was present at high concentrations in fetal rat serum. These results suggest that MCP is a fetal somatomedin carrier protein and that MSA-MCP complexes may be important during fetal development. The availability of antibodies directed against a purified somatomedin carrier protein will provide the opportunity to investigate further the role of carrier proteins in the biological activity of the somatomedins.
一种克隆的大鼠肝细胞系（BRL - 3A）与其特异性载体蛋白（MCP）一起合成并分泌生长调节素，即增殖刺激活性物质（MSA）。亲和纯化的MCP是一种单链多肽，在非还原条件下分子量为31,500，完全还原时为34,000。纯化的MSA（分子量8700）和MCP（分子量34,000）经化学交联后形成分子量为42,000的复合物，这表明基于它们组合分子量的总和，这些成分以1:1的摩尔比结合。还测定了MCP的氨基酸组成和N端氨基酸序列。使用多克隆MCP抗体制剂来确定正常大鼠血清中是否能检测到MCP。在成年大鼠血清中未检测到MCP，但在胎鼠血清中浓度很高。这些结果表明MCP是一种胎儿生长调节素载体蛋白，并且MSA - MCP复合物在胎儿发育过程中可能很重要。针对纯化的生长调节素载体蛋白的抗体的可用性将为进一步研究载体蛋白在生长调节素生物活性中的作用提供机会。
