Morris N J, Ducret A, Aebersold R, Ross S A, Keller S R, Lienhard G E
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
J Biol Chem. 1997 Apr 4;272(14):9388-92. doi: 10.1074/jbc.272.14.9388.
A 97-kDa protein present in the glucose transporter (GLUT4 isotype)-containing vesicles from rat adipocytes has been isolated, the sequences of two tryptic peptides were obtained, and on the basis of these its cDNA partially cloned. The 97-kDa protein is almost certainly identical to a major integral glycoprotein of this size in the rat adipocyte plasma membrane, since its predicted N-terminal sequence is the same as that recently determined for this glycoprotein by amino acid sequencing. Moreover, the predicted partial sequence (322 amino acids) of the 97-kDa protein is highly homologous to the corresponding region of a human placental amine oxidase, which was cloned simultaneously and proposed to be a secreted protein. The amino acid sequence of the 97-kDa rat/human amine oxidase indicates that the protein consists of a very short N-terminal cytoplasmic domain followed by a single transmembrane segment and a large extracellular domain containing the catalytic site. Thus this study establishes the 97-kDa rat/human amine oxidase as the first integral membrane amine oxidase to be cloned. The membrane amine oxidase was more abundant in the plasma membranes than the low density microsomes of the adipocyte, and in contrast to some other proteins found in GLUT4 vesicles, it did not redistribute to the plasma membrane in response to treatment of the cells with insulin.
已从大鼠脂肪细胞中分离出一种存在于含葡萄糖转运蛋白（GLUT4亚型）囊泡中的97 kDa蛋白质，获得了两条胰蛋白酶肽段的序列，并据此对其cDNA进行了部分克隆。该97 kDa蛋白质几乎肯定与大鼠脂肪细胞质膜中这种大小的主要整合糖蛋白相同，因为其预测的N端序列与最近通过氨基酸测序确定的该糖蛋白的序列相同。此外，97 kDa蛋白质的预测部分序列（322个氨基酸）与人类胎盘胺氧化酶的相应区域高度同源，该酶是同时克隆的，并被认为是一种分泌蛋白。97 kDa大鼠/人类胺氧化酶的氨基酸序列表明，该蛋白质由一个非常短的N端胞质结构域、一个单一跨膜片段和一个包含催化位点的大细胞外结构域组成。因此，本研究确定97 kDa大鼠/人类胺氧化酶为第一个被克隆的整合膜胺氧化酶。膜胺氧化酶在脂肪细胞质膜中比低密度微粒体中更丰富，并且与GLUT4囊泡中发现的其他一些蛋白质不同，它不会因用胰岛素处理细胞而重新分布到质膜。
