Wei C L, Kainuma M, Hershey J W
Department of Biological Chemistry, School of Medicine, University of California, Davis 95616, USA.
J Biol Chem. 1995 Sep 29;270(39):22788-94. doi: 10.1074/jbc.270.39.22788.
Translation initiation factor eIF1A is required in vitro for maximal rates of protein synthesis in mammalian systems. It functions primarily by dissociating ribosomes and stabilizing 40 S preinitiation complexes. To better elucidate its precise role in promoting the translation initiation process, the yeast form of eIF1A has been identified in Saccharomyces cerevisiae and purified to homogeneity on the basis of its cross-reaction with antibodies prepared against mammalian eIF1A. The apparent mass of yeast eIF1A (22 kDa) resembles that of the mammalian homolog (20 kDa), and the yeast factor is active in stimulating methionyl-puromycin synthesis in an assay composed of mammalian components. The gene encoding yeast eIF1A, named TIF11, was cloned and shown to be single copy. TIF11 encodes a protein comprising 153 amino acids (17.4 kDa); the deduced amino acid sequence exhibits 65% identity with the sequence of human eIF1A. Both human and yeast eIF1A contain clusters of positive residues at the N terminus and negative residues at the C terminus. Deletion/disruption of TIF11 demonstrates that eIF1A is essential for cell growth. Expression of human eIF1A cDNA rescues the growth defect of TIF11-disrupted cells, indicating that the structure/function of yeast and mammalian eIF1A is highly conserved.
翻译起始因子eIF1A在体外对于哺乳动物系统中蛋白质合成的最大速率是必需的。它主要通过解离核糖体和稳定40S起始前复合物发挥作用。为了更好地阐明其在促进翻译起始过程中的精确作用，已在酿酒酵母中鉴定出eIF1A的酵母形式，并基于其与针对哺乳动物eIF1A制备的抗体的交叉反应将其纯化至同质。酵母eIF1A的表观质量（22 kDa）与哺乳动物同源物（20 kDa）相似，并且在由哺乳动物成分组成的测定中，酵母因子在刺激甲硫氨酰嘌呤霉素合成方面具有活性。编码酵母eIF1A的基因命名为TIF11，已被克隆并显示为单拷贝。TIF11编码一种包含153个氨基酸（17.4 kDa）的蛋白质；推导的氨基酸序列与人类eIF1A的序列具有65%的同一性。人类和酵母eIF1A在N端均含有正电荷残基簇，在C端均含有负电荷残基。TIF11的缺失/破坏表明eIF1A对细胞生长至关重要。人类eIF1A cDNA的表达挽救了TIF11破坏细胞的生长缺陷，表明酵母和哺乳动物eIF1A的结构/功能高度保守。
