Carberry S E, Goss D J
Department of Chemistry, Hunter College, City University of New York 10021-5024.
Biochemistry. 1991 Jul 16;30(28):6977-82. doi: 10.1021/bi00242a024.
The interaction of wheat germ eIF-3 with the wheat germ cap-binding proteins eIF-(iso)4F and eIF-4F as a function of pH and ionic strength is described. Direct fluorescence titration experiments are used to measure the equilibrium association constants (Keq) for the binary protein/protein complexes as well as for the interaction of eIF-3 with methylated cap analogues and rabbit alpha-globin mRNA oligonucleotide analogues. The Keq values for ternary eIF-3/eIF-(iso)4F/analogue and eIF-3/eIF-4F/analogue interactions were also measured. The equilibrium binding constants were used to calculate coupling free energies, which provide an estimate of the cooperativity for the interaction of the mRNA analogues, eIF-3, and either eIF-4F or eIF-(iso)4F. These data suggest a mechanism in which the binding of eIF-(iso)4F or eIF-4F to mRNA enhances the subsequent binding of eIF-3 to the message. This may lead to favorable positioning of the complex on the ribosome and thereby enhance translation.
本文描述了小麦胚芽eIF-3与小麦胚芽帽结合蛋白eIF-(iso)4F和eIF-4F之间的相互作用与pH值和离子强度的关系。采用直接荧光滴定实验来测量二元蛋白质/蛋白质复合物以及eIF-3与甲基化帽类似物和兔α-珠蛋白mRNA寡核苷酸类似物相互作用的平衡缔合常数（Keq）。还测量了三元eIF-3/eIF-(iso)4F/类似物和eIF-3/eIF-4F/类似物相互作用的Keq值。利用平衡结合常数计算耦合自由能，从而估算mRNA类似物、eIF-3以及eIF-4F或eIF-(iso)4F相互作用的协同性。这些数据提示了一种机制，即eIF-(iso)4F或eIF-4F与mRNA的结合增强了随后eIF-3与该信使的结合。这可能导致复合物在核糖体上的有利定位，从而增强翻译。
