摘要
Triose phosphate translocator (TPT) is located in the inner membrane of plant chloroplasts. It catalyzes the counter exchange of those phosphate/3-phosphoglycerate and phosphate. To obtain the basic information on the structure-function relation, a cDNA encoding the complete precursor of the triose phosphate translocator has been isolated from wheat (Triticum aestivum L.) by RACE ( rapid amplification of cDNA ends) strategies. The wheat TPT cDNA encodes a precursor protein of 402 amino acid residues with a deduced molecular weight of 43 kD. A putative processing site between Ala-78 and Ala-79 of the precursor protein is suggested by comparison with those of the TPTs from spinach (Spinacia oleracea Mill.) and maize (Zea mays L.). The mature part of wheat TPT consists of 324 amino acid with a molecular weight of 35 kD, which share 89% identity with maize TPT. The amino acids Lys-274 and Arg-275 (mature protein) which is regarded as the substrate-binding site, are both conserved in plant TPTs. The gene expression analysis for leaves, coleoptiles, roots and seeds of wheat showed that the TPT transcript was only detectable in leaves and coleoptiles. No apparent expression signal was detected in the roots and seeds. This indicated that the expression of wheat TPT might be restricted to green tissues.
利用RT_PCR方法以及RACE(rapidamplificationofcDNAends)策略 ,从小麦 (TriticumaestivumL .)幼苗叶片中克隆了编码磷酸丙糖转运器 (TPT)的全长cDNA。序列分析结果表明 ,小麦TPTcDNA编码 40 2个氨基酸的前体蛋白 ,其中信号肽含有 78个氨基酸。成熟蛋白部分与玉米 (ZeamaysL .)TPT有很高的同源性 (89% )。推测小麦TPT成熟蛋白有 8个跨膜区 ,形成双亲α_螺旋的跨膜结构。位于第 7个跨膜区的Arg_2 74和Lys_2 75可能是底物结合位点。比较TPT基因在小麦幼苗的根、胚芽鞘、叶片和种子中的表达差异表明 :TPT基因在叶片、胚芽鞘中均有表达 ,但在胚芽鞘中的表达量较低 ,在种子和根中未见有表达。由此看来 ,小麦TPT的基因可能只局限在绿色组织中表达。还就C3
基金
国家重点基础研究专项经费资助 (G19980 10 10 0-8G19990 1170 0 )~~
