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Contacts between mammalian mitochondrial translational initiation factor 3 and ribosomal proteins in the small

Md Emdadul Haque1, Hasan Koc, Huseyin Cimen

  • 1Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA.

Biochimica Et Biophysica Acta
|October 22, 2011
PubMed

Insights

Mammalian mitochondrial translational initiation factor 3 (IF3(mt)) binds to the small ribosomal subunit. Cross-linking studies identified novel mitochondrial ribosomal proteins interacting with IF3(mt), including PTCD3.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Mammalian mitochondrial translational initiation factor 3 (IF3(mt)) is crucial for protein biosynthesis initiation.
  • Mitochondrial ribosomes comprise bacterial homologs and unique proteins, with IF3(mt) interacting with the small subunit.

Purpose of the Study:

  • To identify ribosomal proteins in close proximity to the IF3(mt) binding site on the small ribosomal subunit.
  • To characterize the interaction domains of IF3(mt) and its binding partners.

Main Methods:

  • Chemical cross-linking of IF3(mt) to mitochondrial ribosomes.
  • Mass spectrometry for identification of cross-linked proteins.
  • Analysis of truncated IF3(mt) derivatives and isolated domains.

Main Results:

  • IF3(mt) cross-linked to bacterial homologs (S5, S9, S10, S18-2) and unique mitochondrial proteins (MRPS29, MRPS32, MRPS36, PTCD3).
  • PTCD3 (Pet309) was identified as a small subunit ribosomal protein.
  • Truncated IF3(mt) lacking N- and C-terminal extensions showed similar cross-linking, except for MRPS36.
  • The C-domain of IF3(mt) with its linker showed extensive cross-linking to unique mitochondrial proteins.

Conclusions:

  • IF3(mt) interacts with both conserved and unique mitochondrial ribosomal proteins.
  • The N- and C-terminal extensions of IF3(mt) are not essential for binding to most identified proteins.
  • The C-domain and linker region of IF3(mt) play a significant role in binding unique mitochondrial ribosomal proteins.

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