Nombela C, Nombela N A, Ochoa S, Safer B, Anderson W F, Merrick W C
Proc Natl Acad Sci U S A. 1976 Feb;73(2):298-301. doi: 10.1073/pnas.73.2.298.
Artemia salina ribosomal subunits and highly purified reticulocyte initiation factors (IF) are used to study the mechanism of formation of the puromycin-sensitive initiation complex Met-tRNAi-80S ribosome-AUG. A complex with equimolar amounts of 40S subunit, GTP, and Met-tRNAi is formed at low Mg2+ concentration with a requirement for IF-MP (homogeneous) but not AUG or other factors. An 80S complex is formed only upon the further addition of AUG, IF-M2A, and IF-M2B, but not of either factor alone. This complex contains no GTP or GDP. A 40S complex, which cannot be converted to an 80S one, is formed when the nonhydrolyzable analog GMPPCP is substituted for GTP. IF-M2A has no effect on the formation of this complex, but IF-M2B enhances its formation.
卤虫核糖体亚基和高度纯化的网织红细胞起始因子(IF)被用于研究嘌呤霉素敏感起始复合物Met - tRNAi - 80S核糖体 - AUG的形成机制。在低镁离子浓度下,形成了含有等摩尔量40S亚基、GTP和Met - tRNAi的复合物,该过程需要IF - MP(均一的),但不需要AUG或其他因子。只有进一步添加AUG、IF - M2A和IF - M2B时才会形成80S复合物,单独添加任何一个因子都不行。该复合物不包含GTP或GDP。当用不可水解的类似物GMPPCP替代GTP时,会形成一种无法转化为80S复合物的40S复合物。IF - M2A对该复合物的形成没有影响,但IF - M2B会增强其形成。