Danzo B J, Black J H, Bell B W
Department of Obstetrics and Gynecology, Vanderbilt University, Nashville, TN 37232-2633.
J Steroid Biochem Mol Biol. 1991;40(4-6):821-31. doi: 10.1016/0960-0760(91)90308-r.
Rat androgen-binding protein (rABP), human testosterone-binding globulin (hTeBG) and rabbit (rb) TeBG are heterodimeric proteins. The source of the heterogeneity arises from the differential glycosylation of a common protein core. This glycosylation results in a heavy subunit (more glycosylation) and a light subunit (less glycosylation). Glycosylation is one factor responsible for multiple charged species seen when rABP, hTeBG, and rbTeBG are analyzed by two-dimensional gel electrophoresis. Enzymatic digestion with the endoglycosidase, peptide: N-glycosidase F indicated that all three proteins have asparagine (Asn)-linked oligosaccharides as their major glycan substituent. Treatment with exoglycosidases provided evidence for terminal sialic acid, galactose and mannose and N-acetylglucosamine residues. About 16-22% of the mass of the heavy subunit and about 8-14% of the mass of the light subunit is contributed by carbohydrate. Serial lectin chromatography indicated that rABP is glycosylated differently from hTeBG and rbTeBG. About 40% of the rABP contains tri and tetraantennary complex oligosaccharides, while only about 20% of the hTeBG and TeBG from pregnant rabbits contains these types of glycans. About 9% of the TeBG from male rabbits bears these types of oligosaccharides. All of the biantennary complex oligosaccharides on rABP are fucosylated on the chitobiose core, but only 8% of those on hTeBG and none of those on rbTeBG are fucosylated in this manner. All three proteins are glycosylated at more than one site. The data indicate that the proteins may have more than one type of oligosaccharide on them. It is likely that differences in glycosylation are responsible for different physiological roles of the proteins.
大鼠雄激素结合蛋白（rABP）、人睾酮结合球蛋白（hTeBG）和兔（rb）TeBG均为异源二聚体蛋白。这种异质性源于共同蛋白核心的不同糖基化。这种糖基化导致一个重亚基（糖基化程度更高）和一个轻亚基（糖基化程度较低）。糖基化是在通过二维凝胶电泳分析rABP、hTeBG和rbTeBG时出现多种带电物种的一个原因。用内切糖苷酶肽：N-糖苷酶F进行酶切表明，这三种蛋白均以天冬酰胺（Asn）连接的寡糖作为其主要聚糖取代基。用外切糖苷酶处理提供了末端唾液酸、半乳糖、甘露糖和N-乙酰葡糖胺残基的证据。重亚基质量的约16 - 22%和轻亚基质量的约8 - 14%由碳水化合物贡献。连续凝集素层析表明rABP的糖基化与hTeBG和rbTeBG不同。约40%的rABP含有三触角和四触角复合寡糖，而来自怀孕兔子的hTeBG和TeBG中只有约20%含有这些类型的聚糖。来自雄性兔子的TeBG中约9%带有这些类型的寡糖。rABP上所有的双触角复合寡糖在壳二糖核心上都被岩藻糖基化，但hTeBG上只有8%的此类寡糖以及rbTeBG上的此类寡糖均未以这种方式被岩藻糖基化。这三种蛋白均在多个位点进行糖基化。数据表明这些蛋白可能带有不止一种类型的寡糖。糖基化的差异很可能是这些蛋白具有不同生理作用的原因。
