Vanhove B, Goret F, Soulillou J P, Pourcel C
Institut National de la Santé et de la Recherche Médicale U437, Unité de Recherche sur l'Immunointervention dans les Allo et Xénotransplantations, Nantes, France.
Biochim Biophys Acta. 1997 Mar 27;1356(1):1-11. doi: 10.1016/s0167-4889(96)00151-6.
Expression of the Gal alpha1,3 Gal epitope on membrane glycolipids and glycoproteins is known to vary widely from one tissue to another. In the course of studying the mechanisms underlying this variability, we have isolated from pig cDNA four sequences corresponding to four isoforms of alpha1,3-galactosyltransferase (alpha1,3GT), the Golgi enzyme that links galactose in alpha1,3 on the galactose residue of N-acetyllactosamine. The isoforms differ from each other in the alternative presence of two nucleotide stretches of 36 and 63 base pairs in a segment encoding the stem region of the protein. Stable expression experiments show that all four isoenzymes can confer alpha-galactosyltransferase activity to HeLa cells, and that they are all located within the Golgi compartment, indicating that variations in length in the stem region do not affect enzyme activity or cellular localization. Analysis of RNA from different pig organs and cells shows quantitative differences between tissues in levels of alpha1,3GT, as well as qualitative differences, the four isoforms being unequally represented in different tissues.
已知膜糖脂和糖蛋白上α1,3半乳糖表位的表达在不同组织间差异很大。在研究这种变异性潜在机制的过程中，我们从猪cDNA中分离出了四个序列，它们对应于α1,3-半乳糖基转移酶（α1,3GT）的四种同工型，α1,3GT是一种高尔基体酶，能将半乳糖以α1,3连接在N-乙酰乳糖胺的半乳糖残基上。这些同工型在编码蛋白质茎区的一段序列中，交替存在两个分别为36和63个碱基对的核苷酸片段，彼此存在差异。稳定表达实验表明，所有四种同工酶都能赋予HeLa细胞α-半乳糖基转移酶活性，并且它们都定位于高尔基体区室，这表明茎区长度的变化不影响酶活性或细胞定位。对来自不同猪器官和细胞的RNA分析表明，不同组织中α1,3GT水平存在定量差异，也存在定性差异，这四种同工型在不同组织中的表达量不同。
