Schenker T, Lach C, Kessler B, Calderara S, Trueb B
Laboratorium für Biochemie I, Eidenössische Technische Hochschule Zürich, Switzerland.
J Biol Chem. 1994 Oct 14;269(41):25447-53.
We have used a subtractive hybridization procedure to isolate cDNA clones for proteins that are produced by human fibroblasts, but not by their SV40-transformed counterparts. With this technique we found, in addition to fibronectin and collagen VI, a novel GTP-binding protein. Sequencing of overlapping cDNA clones demonstrated that this protein is composed of 364 amino acids with a molecular mass of 41 kDa and a calculated isoelectric point of 9.4. It contains the five sequence motifs G1-G5 that are conserved in all GTP-binding proteins. Apart from these characteristic motifs the amino acid sequence differs substantially from those of the well characterized G-proteins, but it is similar to those of some recently identified proteins from Caenorhabditis elegans, from Schizosaccharomyces pombe, and from an archaebacterium, suggesting the existence of a new subfamily within the superfamily of the GTP-binding proteins. The striking conservation of the primary structure between distantly related species indicates a fundamental function of the new protein. Since it is produced in normal, but not in virally transformed fibroblasts, it may play a role in the expression of the transformed phenotype or in growth control.
我们采用消减杂交技术，分离人成纤维细胞产生但SV40转化的对应细胞不产生的蛋白质的cDNA克隆。利用该技术，我们除了发现纤连蛋白和Ⅵ型胶原外，还发现了一种新型GTP结合蛋白。对重叠cDNA克隆进行测序表明，该蛋白由364个氨基酸组成，分子量为41 kDa，计算的等电点为9.4。它含有在所有GTP结合蛋白中保守的5个序列基序G1 - G5。除了这些特征基序外，其氨基酸序列与已充分表征的G蛋白的序列有很大差异，但与秀丽隐杆线虫、粟酒裂殖酵母和一种古细菌中最近鉴定的一些蛋白质的序列相似，这表明在GTP结合蛋白超家族中存在一个新的亚家族。远缘物种之间一级结构的显著保守性表明该新蛋白具有基本功能。由于它在正常成纤维细胞中产生，而不在病毒转化的成纤维细胞中产生，它可能在转化表型的表达或生长控制中起作用。
