Liu K H, Gao K X, Baumbach G A, Godkin J D
Department of Animal Science, University of Tennessee, Knoxville 37901.
Biol Reprod. 1992 Jan;46(1):23-9. doi: 10.1095/biolreprod46.1.23.
A retinol-binding protein (RBP), synthesized and secreted by ovine allantois in vitro, was purified from culture medium. The protein consisted of three isoelectric variants (pI 5.3-6.1) of identical molecular masses of about 23,000 Da as determined by two-dimensional PAGE under reducing conditions. Thirty-one of the first 34 N-terminal amino acids of the purified protein were sequenced and shown to have complete homology with bovine placental and bovine plasma RBP. The ultraviolet absorption spectrum and fluorescence excitation and emission spectra of the purified ovine placental RBP indicated the presence of bound retinol. Metabolic labeling studies demonstrated that the protein was synthesized by placental membranes. Using antiserum to bovine placental RBP, ovine placental RBP was immunolocalized in trophectoderm of 13-day-old blastocysts and trophectodermal cells of the chorion, endodermal cells lining the allantois, and ectodermal cells lining the amnion of 23-, 45-, and 53-day-old conceptuses. Results from this study suggest that ovine placental membrane epithelia synthesize and secrete RBP. Transport, storage, and metabolism of retinol mediated by placental RBP may be essential for normal embryonic development during pregnancy.
一种由绵羊尿囊体外合成并分泌的视黄醇结合蛋白（RBP）从培养基中被纯化出来。在还原条件下通过二维聚丙烯酰胺凝胶电泳测定，该蛋白由三种等电变体（pI 5.3 - 6.1）组成，分子量相同，约为23,000 Da。对纯化蛋白的前34个N端氨基酸中的31个进行了测序，结果显示其与牛胎盘和牛血浆RBP具有完全同源性。纯化的绵羊胎盘RBP的紫外吸收光谱以及荧光激发和发射光谱表明存在结合的视黄醇。代谢标记研究表明该蛋白由胎盘膜合成。使用针对牛胎盘RBP的抗血清，绵羊胎盘RBP被免疫定位在13日龄胚泡的滋养外胚层、23日龄、45日龄和53日龄孕体的绒毛膜滋养外胚层细胞、尿囊内衬的内胚层细胞以及羊膜内衬的外胚层细胞中。本研究结果表明绵羊胎盘膜上皮细胞合成并分泌RBP。胎盘RBP介导的视黄醇的转运、储存和代谢可能对孕期正常胚胎发育至关重要。
