Bröer A, Hamprecht B, Bröer S
Physiologisch-Chemisches Institut, Universität Tübingen, Hoppe-Seyler Strasse 4, 72076 Tübingen, Germany.
Biochem J. 1998 Aug 1;333 ( Pt 3)(Pt 3):549-54. doi: 10.1042/bj3330549.
Expression of the type II membrane proteins of the rbAT/4F2hc family in Xenopus laevis oocytes results in the induction of amino acid transport activity. To elucidate the mechanism of action, amino acid transport was investigated in oocytes expressing the surface antigen 4F2hc. Leucine transport was mediated by a Na+-independent and a Na+-dependent transport mechanism. Both systems could be further discriminated by their stereochemical constraints. Isoleucine, with a branch at the beta-position, shared only the Na+-independent transport system with leucine. Both transport systems were sensitive to inhibition by arginine, but only the Na+-independent system was sensitive to inhibition by 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid. When compared with known transport systems the two transport activities could be described as similar to, but not identical with, mammalian systems b0,+ and y+L. The Na+-independent b0,+-like transport system was found both in rbAT and 4F2hc expressing oocytes, indicating that both proteins act in a similar way.
rbAT/4F2hc家族的II型膜蛋白在非洲爪蟾卵母细胞中的表达导致氨基酸转运活性的诱导。为阐明其作用机制，对表达表面抗原4F2hc的卵母细胞中的氨基酸转运进行了研究。亮氨酸转运由不依赖Na⁺和依赖Na⁺的转运机制介导。这两种系统可通过其立体化学限制进一步区分。在β位有分支的异亮氨酸仅与亮氨酸共享不依赖Na⁺的转运系统。两种转运系统均对精氨酸抑制敏感，但只有不依赖Na⁺的系统对2-氨基双环[2,2,1]庚烷-2-羧酸抑制敏感。与已知转运系统相比，这两种转运活性可描述为与哺乳动物系统b0,+和y+L相似但不相同。在表达rbAT和4F2hc的卵母细胞中均发现了不依赖Na⁺的b0,+样转运系统，表明这两种蛋白的作用方式相似。
