Wang M Y, Tsai M Y, Wang C
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
Arch Biochem Biophys. 1994 Apr;310(1):172-9. doi: 10.1006/abbi.1994.1154.
A cDNA, Ch-GT2, encoding a glucose transporter was cloned by screening a chicken liver lambda gt11 cDNA library and by modified polymerase chain reaction (PCR) techniques. The encoded protein is highly homologous to rat and human GLUT 2. Within the predicted amino acid sequence, there are 12 putative transmembrane helices with a relatively large exofacial hydrophilic loop between transmembrane segments 1 and 2, which is characteristic of mammalian GLUT 2. Expression of Ch-GT2 gene in E. coli results in sixfold increase in the uptake of 2-deoxy-D-glucose uptake, and this increment can be reduced by incubation with phloretin. Thus, Ch-GT2 is a bona fide chicken liver glucose transporter. A deletion mutant generated by PCR was expressed in bacteria and shown to be functional, indicating that the N-terminal seven amino acid residues of Ch-GT2 is not essential for transport of glucose. From Northern blot analysis, Ch-GT2 is prominently expressed in chicken liver with a transcript of 4.0 kb, but not in chicken brain and heart, suggesting that distinct types of glucose transporters are present in various chicken tissues.
通过筛选鸡肝λgt11 cDNA文库并采用改良的聚合酶链反应（PCR）技术，克隆出了一个编码葡萄糖转运蛋白的cDNA，即Ch-GT2。所编码的蛋白质与大鼠和人类的GLUT 2高度同源。在预测的氨基酸序列中，有12个假定的跨膜螺旋，在跨膜片段1和2之间有一个相对较大的胞外亲水环，这是哺乳动物GLUT 2的特征。Ch-GT2基因在大肠杆菌中的表达导致2-脱氧-D-葡萄糖摄取增加了六倍，并且这种增加可以通过与根皮素孵育而降低。因此，Ch-GT2是一种真正的鸡肝葡萄糖转运蛋白。通过PCR产生的缺失突变体在细菌中表达并显示具有功能，这表明Ch-GT2的N端七个氨基酸残基对于葡萄糖转运不是必需的。从Northern印迹分析来看，Ch-GT2在鸡肝中显著表达，转录本为4.0 kb，但在鸡脑和心脏中不表达，这表明不同类型的葡萄糖转运蛋白存在于鸡的各种组织中。
