Balasta M L, Carberry S E, Friedland D E, Perez R A, Goss D J
Department of Chemistry, Hunter College, City University of New York, New York 10021-5024.
J Biol Chem. 1993 Sep 5;268(25):18599-603.
The ATP-dependent binding of wheat germ protein synthesis initiation factors eIF-(iso)4F and eIF-4A to an oligoribonucleotide has been investigated by direct fluorescence titration techniques. In addition, the effect of ATP on the interaction between another cap-binding initiation factor, eIF-4F, and eIF-4A was studied using the same methods. Comparison of the equilibrium association constants (K(eq)) indicate that 1) hydrolyzable ATP affects the affinity of eIF-(iso)4F for eIF-4A, regardless of whether or not mRNA was previously bound to the eIF-(iso)4F; in contrast, ATP had no effect on the eIF-(iso)4F/oligoribonucleotide interaction; 2) in the presence of ATP, the binding of the binary eIF-(iso)4F.eIF-4A complex to the oligoribonucleotide is of similar affinity as the binding of the oligoribonucleotide to the eIF-(iso)4F alone; the stoichiometry of this ternary eIF-(iso)4F.eIF-4A.mRNA complex was found to be 1:1:1; and 3) a similar ATP effect is observed for the eIF-4F/eIF-4A interaction as for the eIF-(iso)4F.eIF-4A complex.
通过直接荧光滴定技术研究了小麦胚芽蛋白合成起始因子eIF-(iso)4F和eIF-4A与寡核糖核苷酸的ATP依赖性结合。此外，使用相同方法研究了ATP对另一种帽结合起始因子eIF-4F和eIF-4A之间相互作用的影响。平衡缔合常数（K(eq)）的比较表明：1）可水解的ATP会影响eIF-(iso)4F对eIF-4A的亲和力，无论mRNA之前是否与eIF-(iso)4F结合；相反，ATP对eIF-(iso)4F/寡核糖核苷酸相互作用没有影响；2）在ATP存在下，二元eIF-(iso)4F.eIF-4A复合物与寡核糖核苷酸的结合亲和力与寡核糖核苷酸单独与eIF-(iso)4F的结合亲和力相似；发现这种三元eIF-(iso)4F.eIF-4A.mRNA复合物的化学计量比为1:1:1；3）对于eIF-4F/eIF-4A相互作用，观察到与eIF-(iso)4F.eIF-4A复合物类似的ATP效应。
