Viel A, le Maire M, Philippe H, Morales J, Mazabraud A, Denis H
Centre de Génétique Moléculaire, Laboratoire propre du Centre National de la Recherche Scientifique (CNRS) associé à l'Université P. et M. Curie, Gif-sur-Yvette, France.
J Biol Chem. 1991 Jun 5;266(16):10392-9.
Thesaurin a is one of two protein components of a 42 S ribonucleoprotein particle that is very abundant in previtellogenic oocytes of Xenopus laevis. The primary function of the 42 S particle is the long-term storage of 5 S RNA and aminoacyl-tRNA. Thesaurin a is homologous to eukaryotic elongation factor 1 alpha (EF-1 alpha) and to prokaryotic elongation factor Tu (EF-Tu). Sequence comparison with EF-1 alpha and EF-Tu of different species indicates that thesaurin a is rather distantly related to all eukaryotic elongation factors. In spite of this, the secondary structure of thesaurin a, deduced from hydrophobic cluster analysis, is remarkably similar to that of EF-1 alpha and EF-Tu. The binding and catalytic properties of thesaurin a are also similar but not identical to those of EF-1 alpha. Like EF-1 alpha, purified thesaurin a binds tRNA, GDP, and GTP. Unlike EF-1 alpha, thesaurin a binds discharged tRNA more tightly than charged tRNA, and GTP more tightly than GDP. Thesaurin a also hydrolyzes GTP and catalyzes the mRNA-dependent binding of aminoacyl-tRNA to 80 S ribosomes. The functional properties of the 42 S particle are in general agreement with those of purified thesaurin a. In particular, the 42 S particle contains GTP and efficiently transfers aminoacyl-tRNA to 80 S ribosomes without addition of exogenous elongation factor.
Thesaurin a是42S核糖核蛋白颗粒的两种蛋白质成分之一，该颗粒在非洲爪蟾的卵黄发生前卵母细胞中含量非常丰富。42S颗粒的主要功能是5S RNA和氨酰tRNA的长期储存。Thesaurin a与真核延伸因子1α（EF-1α）和原核延伸因子Tu（EF-Tu）同源。与不同物种的EF-1α和EF-Tu的序列比较表明，Thesaurin a与所有真核延伸因子的关系相当疏远。尽管如此，通过疏水簇分析推导的Thesaurin a的二级结构与EF-1α和EF-Tu的二级结构非常相似。Thesaurin a的结合和催化特性也与EF-1α相似但不完全相同。与EF-1α一样，纯化的Thesaurin a结合tRNA、GDP和GTP。与EF-1α不同的是，Thesaurin a与空载tRNA的结合比与负载tRNA的结合更紧密，与GTP的结合比与GDP的结合更紧密。Thesaurin a还能水解GTP并催化氨酰tRNA与80S核糖体的mRNA依赖性结合。42S颗粒的功能特性总体上与纯化的Thesaurin a的功能特性一致。特别是，42S颗粒含有GTP，并且在不添加外源延伸因子的情况下能有效地将氨酰tRNA转移到80S核糖体上。
