Chakraburtty K, Triana-Alonso F J
Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226, USA.
Biol Chem. 1998 Jul;379(7):831-40. doi: 10.1515/bchm.1998.379.7.831.
Elongation factor 3 (EF-3) is a unique and essential requirement of the fungal translational apparatus. EF-3 is a single polypeptide protein with a molecular weight of 116,000 required by yeast ribosomes for in vitro translation and for in vivo growth. The YEF3 gene, located on chromosome xii, is essential for the survival of yeast. The deduced amino acid sequence of EF-3 has revealed the presence of duplicated ATP-binding cassettes similar to those present in the membrane associated transporters. The carboxy-terminus of EF-3 contains blocks of lysine boxes essential for its functional interaction with yeast ribosomes. EF-3 stimulates binding of aminoacyl-tRNA to the ribosomal A-site by facilitating release of deacylated tRNA from the exit site (E-site). Chasing experiments revealed that EF-3 enhances the rate of tRNA dissociation from the E-site by a factor of two without affecting the affinity of the site for tRNA. EF-3 function is dependent on ATP hydrolysis. The existence of functional homologs of EF-3 in higher eukaryotes is still an open question. Further investigations are needed to settle this issue.
延伸因子3（EF-3）是真菌翻译装置所特有的且必不可少的成分。EF-3是一种单链多肽蛋白，分子量为116,000，酵母核糖体在体外翻译和体内生长时都需要它。位于第十二号染色体上的YEF3基因对酵母的存活至关重要。EF-3推导的氨基酸序列显示存在与膜相关转运蛋白中类似的重复ATP结合盒。EF-3的羧基末端包含对其与酵母核糖体功能相互作用至关重要的赖氨酸盒结构域。EF-3通过促进脱酰基tRNA从核糖体E位点释放，刺激氨酰tRNA与核糖体A位点的结合。追踪实验表明，EF-将tRNA从E位点解离的速率提高了两倍，而不影响该位点对tRNA的亲和力。EF-3的功能依赖于ATP水解。高等真核生物中是否存在EF-3的功能同源物仍是一个悬而未决的问题。需要进一步研究来解决这个问题。
