Antony A C, Utley C, Van Horne K C, Kolhouse J F
J Biol Chem. 1981 Sep 25;256(18):9684-92.
While folate binding proteins have been described in serum and a variety of tissues, the function of these proteins is unknown. A particulate folate binding protein from human placenta has been isolated and characterized following solubilization with Triton X-100. The protein was purified 61,000-fold using affinity chromatography on pteroylglutamic acid-Sepharose as the major purification step. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified protein gave a single band with a Mr = 38,500. Stoichiometry of binding indicated that 1 mol of folate was bound per mol of protein. The protein was a glycoprotein that contained 12% carbohydrate. Antiserum was raised in a rabbit, and on immunodiffusion, gave a single precipitin line with the purified placental folate binding protein. Immunoprecipitation studies using this antiserum indicated that the purified placental folate binding protein shared antigenic determinants with both the large Mr and small Mr folate binding proteins from human milk. Immunofluorescent studies with this antiserum and human erythrocytes revealed the presence of an immunologically similar protein on the plasma membrane of these cells suggesting that this protein may function as a folate receptor.
虽然在血清和多种组织中已发现叶酸结合蛋白，但这些蛋白的功能尚不清楚。用 Triton X - 100 增溶后，已从人胎盘中分离并鉴定出一种颗粒状叶酸结合蛋白。以蝶酰谷氨酸 - 琼脂糖亲和层析作为主要纯化步骤，该蛋白被纯化了 61000 倍。在十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳上，纯化后的蛋白呈现出一条 Mr = 38500 的单带。结合化学计量表明，每摩尔蛋白结合 1 摩尔叶酸。该蛋白是一种糖蛋白，含 12%的碳水化合物。用兔制备了抗血清，在免疫扩散实验中，与纯化的胎盘叶酸结合蛋白产生了一条单一的沉淀线。使用该抗血清的免疫沉淀研究表明，纯化的胎盘叶酸结合蛋白与人乳中 Mr 大的和 Mr 小的叶酸结合蛋白具有共同的抗原决定簇。用该抗血清和人红细胞进行的免疫荧光研究显示，这些细胞的质膜上存在一种免疫相似的蛋白，提示该蛋白可能作为叶酸受体发挥作用。
