Checkley J W, Cooley L, Ravel J M
J Biol Chem. 1981 Feb 25;256(4):1582-6.
Initiation factor eIF-3 has been isolated from the 120 mM KCl postribosomal supernatant of wheat germ by chromatography on DEAE-cellulose and phosphocellulose. Glycerol gradient centrifugation and polyacrylamide gel electrophoresis under nondenaturing conditions indicate that the eIF-3 prepared in this manner is at least 85% pure. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate shows that the wheat germ eIF-3 contains 11 polypeptides, ranging in molecular weight from about 25,000 to 120,000. Eight of the polypeptides are present in equimolar amounts; two of the polypeptides are present at molar ratios of about 0.5; and one is present at a molar ratio of about 0.3. The highly purified wheat germ eIF-3 does not prevent the association of wheat germ 40S and 60 S ribosomal subunits to a significant extent. Wheat germ eIF-3 does not increase appreciably the ability of eIF-2 to form a ternary complex with Met-tRNAf and GTP. It does, however, enhance the binding of Met-tRNAf to 40 S ribosomal subunits in the presence of eIF-2 and GTP.
起始因子eIF-3已通过在DEAE-纤维素和磷酸纤维素上进行色谱分离，从小麦胚芽120 mM KCl核糖体后上清液中分离出来。甘油梯度离心和非变性条件下的聚丙烯酰胺凝胶电泳表明，以这种方式制备的eIF-3纯度至少为85%。十二烷基硫酸钠存在下的聚丙烯酰胺凝胶电泳显示，小麦胚芽eIF-3含有11种多肽，分子量范围约为25,000至120,000。其中8种多肽以等摩尔量存在；2种多肽以约0.5的摩尔比存在；1种多肽以约0.3的摩尔比存在。高度纯化的小麦胚芽eIF-3在很大程度上不会阻止小麦胚芽40S和60S核糖体亚基的结合。小麦胚芽eIF-3不会显著提高eIF-2与Met-tRNAf和GTP形成三元复合物的能力。然而，在eIF-2和GTP存在的情况下，它确实会增强Met-tRNAf与40S核糖体亚基的结合。
