Drew J E, Bown D, Gatehouse J A
Department of Biological Sciences, University of Durham, UK.
Plant Mol Biol. 1993 Mar;21(6):1195-9. doi: 10.1007/BF00023617.
A clone isolated from a purple podded pea (Pisum sativum L.) cDNA library was shown to contain the complete coding sequence of a polypeptide with considerable homology to various members of the ras superfamily. The ras superfamily are a group of monomeric GTP-binding proteins of 21-25 kDa found in eukaryotic cells. Conserved sequences in the isolated clone include the GTP-binding site, GDP/GTP hydrolysis domain and C-terminal Cys residues involved in membrane attachment. Comparisons of the predicted amino acid sequence with those of other ras proteins show significantly higher homologies (ca. 70%) to two mammalian gene products, those of the BRL-ras oncogene, and the canine rab7 gene, than to any of the plant ras gene products so far identified (< 40% homology). The high percentage of amino acid identity suggests that this cDNA may be the product of a gene, designated Psa-rab, which is the plant counterpart of rab7. Rab/ypt proteins are a subfamily of the ras superfamily thought to be involved in intracellular transport from the endoplasmic reticulum to the Golgi apparatus and in vesicular transport. Northern blot hybridisation analysis of total RNA from green and purple podded pea revealed a mRNA species of approximately the same size as the isolated cDNAs.
从紫色豆荚豌豆（Pisum sativum L.）cDNA文库中分离出的一个克隆，被证明含有一种多肽的完整编码序列，该多肽与ras超家族的各个成员具有相当高的同源性。ras超家族是在真核细胞中发现的一组分子量为21 - 25 kDa的单体GTP结合蛋白。分离出的克隆中的保守序列包括GTP结合位点、GDP/GTP水解结构域以及参与膜附着的C末端半胱氨酸残基。将预测的氨基酸序列与其他ras蛋白的序列进行比较，结果显示，与两种哺乳动物基因产物（BRL - ras癌基因产物和犬rab7基因产物）的同源性显著更高（约70%），而与迄今为止鉴定出的任何植物ras基因产物的同源性较低（<40%同源性）。高比例的氨基酸同一性表明，这个cDNA可能是一个名为Psa - rab的基因的产物，它是rab7的植物对应物。Rab/ypt蛋白是ras超家族的一个亚家族，被认为参与从内质网到高尔基体的细胞内运输以及囊泡运输。对绿色和紫色豆荚豌豆的总RNA进行Northern印迹杂交分析，结果显示有一种mRNA，其大小与分离出的cDNA大致相同。
