Interaction between eukaryotic initiation factors 1A and 5B is required for efficient ribosomal subunit joining
Interaction between eukaryotic initiation factors 1A and 5B is required for efficient ribosomal subunit joining
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DOI：
10.1074/jbc.m600210200
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发表时间：
2006-03-31
影响因子：
4.8
通讯作者：
Lorsch, JR
中科院分区：
文献类型：
--
作者：
Acker, MG;Shin, BS;Lorsch, JR
真核起始因子5 B（eIF 5 B）是一种在翻译起始过程中促进60 S核糖体亚基与40 S核糖体亚基连接的GTP酶。所产生的80 S起始复合物的形成触发eIF 5 B水解其结合的GTP，降低因子对复合物的亲和力并使其解离。在这里，我们提出了一个动力学分析的GTP水解eIF 5 B的翻译起始途径的背景下。我们的数据表明，刺激GTP水解的eIF 5 B需要完成翻译起始的早期步骤，包括eIF 1-和eIF 1A-依赖性交付的起始甲硫氨酰- tRNA的40 S核糖体亚基和随后的GTP水解的eIF 2。通过eIF 5 B完全激活GTP水解需要eIF 1A的极端C末端，其先前已显示与eIF 5 B的C末端相互作用。破坏eIF 1A C-末端序列DIDDI中的任一异亮氨酸残基可使GTP水解的速率常数降低约20倍，而改变天冬氨酸残基则没有影响。改变eIF 1A C末端的异亮氨酸也破坏了eIF 5 B促进亚基连接的能力。这些数据表明eIF 1A的C末端与eIF 5 B的相互作用促进核糖体亚基连接，并可能为正确的复合物形成提供检查点，仅在形成正确组织的80 S起始复合物时才允许完全激活GTP水解。
Eukaryotic initiation factor 5B ( eIF5B) is aGTPase that facilitates joining of the 60 S ribosomal subunit to the 40 S ribosomal subunit during translation initiation. Formation of the resulting 80 S initiation complex triggers eIF5B to hydrolyze its bound GTP, reducing the affinity of the factor for the complex and allowing it to dissociate. Here we present a kinetic analysis of GTP hydrolysis by eIF5B in the context of the translation initiation pathway. Our data indicate that stimulation of GTP hydrolysis by eIF5B requires the completion of early steps in translation initiation, including the eIF1- and eIF1A- dependent delivery of initiator methionyl- tRNA to the 40 S ribosomal subunit and subsequent GTP hydrolysis by eIF2. Full activation of GTP hydrolysis by eIF5B requires the extreme C terminus of eIF1A, which has previously been shown to interact with the C terminus of eIF5B. Disruption of either isoleucine residue in the eIF1A C- terminal sequence DIDDI reduces the rate constant for GTP hydrolysis by similar to 20- fold, whereas changing the aspartic acid residues has no effect. Changing the isoleucines in the C terminus of eIF1A also disrupts the ability of eIF5B to facilitate subunit joining. These data indicate that the interaction of the C terminus of eIF1A with eIF5B promotes ribosomal subunit joining and possibly provides a checkpoint for correct complex formation, allowing full activation of GTP hydrolysis only upon formation of a properly organized 80 S initiation complex.