Kwong F Y, Baldwin S A, Scudder P R, Jarvis S M, Choy M Y, Young J D
Biochem J. 1986 Dec 1;240(2):349-56. doi: 10.1042/bj2400349.
Nucleoside- and glucose-transport proteins isolated from human erythrocyte membranes were photoaffinity-labelled with [3H]nitrobenzylthioinosine and [3H]cytochalasin B, respectively, and subjected to endo-beta-galactosidase or endoglycosidase-F digestion. Without enzyme treatment the two radiolabelled transporters migrated on SDS/polyacrylamide gels with the same apparent Mr (average) of 55,000. Apparent Mr (average) values after endo-beta-galactosidase digestion were 47,000 and 48,000 for the nucleoside and glucose transporters respectively, and 44,000 and 45,000 respectively after endoglycosidase-F digestion. In contrast, endo-beta-galactosidase had no effect on the electrophoretic mobility of the nucleoside transporter isolated from pig erythrocytes. This transport system exhibited a higher Mr than the human protein, endoglycosidase-F treatment decreasing its apparent Mr (average) from 64,000 to 57,000. It is concluded that the human and pig erythrocyte nucleoside transporters are glycoproteins containing N-linked oligosaccharide. The data provide evidence of substantial carbohydrate and polypeptide differences between the human and pig erythrocyte nucleoside transporters, but evidence of molecular similarities between the human erythrocyte nucleoside and glucose transporters.
从人红细胞膜中分离出的核苷转运蛋白和葡萄糖转运蛋白，分别用[³H]硝基苄硫肌苷和[³H]细胞松弛素B进行光亲和标记，然后用内切β-半乳糖苷酶或内切糖苷酶F消化。未经酶处理时，两种放射性标记的转运蛋白在SDS/聚丙烯酰胺凝胶上迁移，表观相对分子质量（平均值）均为55,000。经内切β-半乳糖苷酶消化后，核苷转运蛋白和葡萄糖转运蛋白的表观相对分子质量（平均值）分别为47,000和48,000，经内切糖苷酶F消化后分别为44,000和45,000。相比之下，内切β-半乳糖苷酶对从猪红细胞中分离出的核苷转运蛋白的电泳迁移率没有影响。该转运系统的相对分子质量高于人源蛋白，经内切糖苷酶F处理后，其表观相对分子质量（平均值）从64,000降至57,000。结论是人红细胞和猪红细胞核苷转运蛋白是含N-连接寡糖的糖蛋白。这些数据证明了人红细胞和猪红细胞核苷转运蛋白在碳水化合物和多肽方面存在显著差异，但也证明了人红细胞核苷转运蛋白和葡萄糖转运蛋白之间存在分子相似性。
