Purification and characterization of yeast mitochondrial initiation factor 2

Area of Science:

• Molecular Biology
• Protein Biochemistry
• Mitochondrial Translation

Background:

• Yeast mitochondrial initiation factor 2 (ymIF2), encoded by the nuclear IFM1 gene, plays a crucial role in mitochondrial protein synthesis.
• Understanding the biochemical properties of ymIF2 is essential for elucidating the mechanisms of mitochondrial translation initiation.

Purpose of the Study:

• To characterize the biochemical properties of purified yeast mitochondrial initiation factor 2 (ymIF2).
• To compare the functional activities of ymIF2 with those of Escherichia coli IF2.

Main Methods:

• Expression and purification of a His-tagged ymIF2 lacking its mitochondrial presequence in E. coli.
• In vitro assays to assess initiator tRNA binding, ribosomal binding, GTPase activity, and protection against deacylation.
• Comparison of ymIF2 with E. coli IF2 in gel shift assays and analysis of N-terminal domain deletion effects.

Main Results:

• Purified ymIF2 demonstrated higher binding affinity for formylated initiator tRNA (fMet-tRNA(f)(Met)) compared to unformylated Met-tRNA(f)(Met).
• ymIF2 exhibited ribosome-dependent GTPase activity and protected fMet-tRNA(f)(Met) from deacylation, similar to E. coli IF2.
• The complex of ymIF2 and fMet-tRNA(f)(Met) was less stable than that of E. coli IF2, and the N-terminal domain was dispensable for tRNA binding.

Conclusions:

• Yeast mitochondrial initiation factor 2 exhibits functional characteristics analogous to bacterial IF2, including preferential binding of formylated initiator tRNA.
• The study provides insights into the conserved and divergent aspects of translation initiation factors across different organisms and organelles.