Gaur Rahul, Grasso Domenick, Datta Partha P, Krishna P D V, Das Gautam, Spencer Angela, Agrawal Rajendra K, Spremulli Linda, Varshney Umesh
Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
Mol Cell. 2008 Feb 1;29(2):180-90. doi: 10.1016/j.molcel.2007.11.021.
The mechanism of translation in eubacteria and organelles is thought to be similar. In eubacteria, the three initiation factors IF1, IF2, and IF3 are vital. Although the homologs of IF2 and IF3 are found in mammalian mitochondria, an IF1 homolog has never been detected. Here, we show that bovine mitochondrial IF2 (IF2(mt)) complements E. coli containing a deletion of the IF2 gene (E. coli DeltainfB). We find that IF1 is no longer essential in an IF2(mt)-supported E. coli DeltainfB strain. Furthermore, biochemical and molecular modeling data show that a conserved insertion of 37 amino acids in the IF2(mt) substitutes for the function of IF1. Deletion of this insertion from IF2(mt) supports E. coli for the essential function of IF2. However, in this background, IF1 remains essential. These observations provide strong evidence that a single factor (IF2(mt)) in mammalian mitochondria performs the functions of two eubacterial factors, IF1 and IF2.
人们认为真细菌和细胞器中的翻译机制是相似的。在真细菌中，三种起始因子IF1、IF2和IF3至关重要。虽然在哺乳动物线粒体中发现了IF2和IF3的同源物，但从未检测到IF1的同源物。在此，我们表明牛线粒体IF2（IF2(mt)）可补充缺失IF2基因的大肠杆菌（大肠杆菌ΔinfB）。我们发现，在由IF2(mt)支持的大肠杆菌ΔinfB菌株中，IF1不再是必需的。此外，生化和分子建模数据表明，IF2(mt)中一个由37个氨基酸组成的保守插入片段替代了IF1的功能。从IF2(mt)中删除此插入片段后，大肠杆菌仍能支持IF2的基本功能。然而，在此背景下，IF1仍然是必需的。这些观察结果提供了强有力的证据，表明哺乳动物线粒体中的单一因子（IF2(mt)）执行了真细菌中两个因子IF1和IF2的功能。
