Slobin L I
J Biol Chem. 1983 Apr 25;258(8):4895-900.
The binding of eucaryotic elongation factor Tu (eEF-Tu) to nucleic acids was investigated. eEF-Tu binds to a variety of different nucleic acids with high affinity, showing a strong preference for 18 S and 28 S rRNA over transfer RNA and for ribose-containing polymers over polydeoxyribonucleotides. The factor binds at multiple sites on 28 S rRNA without strong cooperativity. eEF-Tu binds strongly to poly(G) and poly(U) but weakly, if at all, to poly(A) and poly(C). Experiments employing an airfuge demonstrate that eEF-Tu can form a quaternary complex containing the factor, 28 S rRNA, aminoacyl-tRNA, and GTP. The existence of two distinct RNA binding sites on eEF-Tu suggests that rRNA may play a role in the recognition of eEF-Tu.aminoacyl-tRNA.GTP complexes by polysomes. Support for this suggestion comes from experiments which show that poly(G) inhibits the factor-dependent binding of aminoacyl-tRNA to mRNA-programmed 80 S ribosomes. In addition, it is shown that eEF-Tu possesses an intrinsic GTPase activity which is stimulated significantly by 28 S rRNA, poly(G), and poly(U). The binding of eEF-Tu to poly(G) lowers the activation energy for eEF-Tu GTPase from 74.3 to 65.9 kJ . mol-1 and approximately doubles the Vmax of the enzymatic reaction. The results are discussed in relation to the binding of eEF-Tu to ribosomes during protein synthesis.
对真核生物延伸因子Tu（eEF-Tu）与核酸的结合进行了研究。eEF-Tu以高亲和力结合多种不同的核酸，相较于转运RNA，它对18 S和28 S核糖体RNA表现出强烈偏好，对含核糖的聚合物的偏好高于多脱氧核糖核苷酸。该因子在28 S核糖体RNA的多个位点结合，且无强协同性。eEF-Tu与聚鸟苷酸（poly(G)）和聚尿苷酸（poly(U)）强烈结合，但与聚腺苷酸（poly(A)）和聚胞苷酸（poly(C)）结合较弱（若有结合的话）。采用空气离心机的实验表明，eEF-Tu可形成一种包含该因子、28 S核糖体RNA、氨酰-tRNA和鸟苷三磷酸（GTP）的四元复合物。eEF-Tu上存在两个不同的RNA结合位点，这表明核糖体RNA可能在多核糖体识别eEF-Tu·氨酰-tRNA·GTP复合物中发挥作用。这一推测得到了实验支持，实验表明聚鸟苷酸抑制氨酰-tRNA与mRNA编程的80 S核糖体的因子依赖性结合。此外，研究表明eEF-Tu具有内在的GTP酶活性，28 S核糖体RNA、聚鸟苷酸和聚尿苷酸可显著刺激该活性。eEF-Tu与聚鸟苷酸的结合将eEF-Tu GTP酶的活化能从74.3 kJ·mol-1降至65.9 kJ·mol-1，并使酶促反应的最大反应速度（Vmax）增加约一倍。结合蛋白质合成过程中eEF-Tu与核糖体的结合对这些结果进行了讨论。
