Wang H, Huang W, Sugawara M, Devoe L D, Leibach F H, Prasad P D, Ganapathy V
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912, USA.
Biochem Biophys Res Commun. 2000 Jul 14;273(3):1175-9. doi: 10.1006/bbrc.2000.3061.
This report describes the primary structure and functional characteristics of human ATA1, a subtype of the amino acid transport system A. The human ATA1 cDNA was isolated from a placental cDNA library. The cDNA codes for a protein of 487 amino acids with 11 putative transmembrane domains. The transporter mRNA ( approximately 9.0 kb) is expressed most prominently in the placenta and heart, but detectable level of expression is evident in other tissues including the brain. When expressed heterologously in mammalian cells, the cloned transporter mediates Na(+)-coupled transport of the system A-specific model substrate alpha-(methylamino)isobutyric acid. The transport process is saturable with a Michaelis-Menten constant of 0. 89 +/- 0.12 mM. The Na(+):amino acid stoichiometry is 1:1 as deduced from the Na(+)-activation kinetics. The transporter is specific for small short-chain neutral amino acids. The gene for the transporter is located on human chromosome 12.
本报告描述了氨基酸转运系统A的一个亚型——人ATA1的一级结构和功能特性。人ATA1 cDNA是从胎盘cDNA文库中分离得到的。该cDNA编码一个含有487个氨基酸、具有11个推定跨膜结构域的蛋白质。转运体mRNA（约9.0 kb）在胎盘和心脏中表达最为显著，但在包括脑在内的其他组织中也能检测到明显的表达水平。当在哺乳动物细胞中异源表达时，克隆的转运体介导系统A特异性模型底物α-（甲基氨基）异丁酸的Na⁺偶联转运。转运过程是可饱和的，米氏常数为0.89±0.12 mM。从Na⁺激活动力学推导，Na⁺:氨基酸化学计量比为1:1。该转运体对小的短链中性氨基酸具有特异性。该转运体的基因位于人类12号染色体上。
