Structural highlights
Function
[IF3M_HUMAN] IF-3 binds to the 28S ribosomal subunit and shifts the equilibrum between 55S ribosomes and their 39S and 28S subunits in favor of the free subunits, thus enhancing the availability of 28S subunits on which protein synthesis initiation begins.[1] [RT34_BOVIN] Required for mitochondrial translation, plays a role in maintaining the stability of the small ribosomal subunit and the 12S rRNA that are required for mitoribosome formation.[UniProtKB:Q9JIK9] [PTCD3_BOVIN] Mitochondrial RNA-binding protein that has a role in mitochondrial translation.
Publication Abstract from PubMed
The human mitochondrial translational initiation factor 3 (IF3mt) carries mitochondrial-specific amino acid extensions at both its N and C termini (N- and C-terminal extensions [NTE and CTE, respectively]), when compared with its eubacterial counterpart. Here we present 3.3- to 3.5-A-resolution cryoelectron microscopic structures of the mammalian 28S mitoribosomal subunit in complex with human IF3mt. Unique contacts observed between the 28S subunit and N-terminal domain of IF3mt explain its unusually high affinity for the 28S subunit, whereas the position of the mito-specific NTE suggests NTE's role in binding of initiator tRNA to the 28S subunit. The location of the C-terminal domain (CTD) clarifies its anti-association activity, whereas the orientation of the mito-specific CTE provides a mechanistic explanation for its role in destabilizing initiator tRNA in the absence of mRNA. Furthermore, our structure hints at a possible role of the CTD in recruiting leaderless mRNAs for translation initiation. Our findings highlight unique features of IF3mt in mitochondrial translation initiation.
Structure of Human Mitochondrial Translation Initiation Factor 3 Bound to the Small Ribosomal Subunit.,Koripella RK, Sharma MR, Haque ME, Risteff P, Spremulli LL, Agrawal RK iScience. 2019 Feb 22;12:76-86. doi: 10.1016/j.isci.2018.12.030. Epub 2019 Jan 3. PMID:30677741[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Koc EC, Spremulli LL. Identification of mammalian mitochondrial translational initiation factor 3 and examination of its role in initiation complex formation with natural mRNAs. J Biol Chem. 2002 Sep 20;277(38):35541-9. doi: 10.1074/jbc.M202498200. Epub 2002 , Jul 2. PMID:12095986 doi:http://dx.doi.org/10.1074/jbc.M202498200
- ↑ Koripella RK, Sharma MR, Haque ME, Risteff P, Spremulli LL, Agrawal RK. Structure of Human Mitochondrial Translation Initiation Factor 3 Bound to the Small Ribosomal Subunit. iScience. 2019 Feb 22;12:76-86. doi: 10.1016/j.isci.2018.12.030. Epub 2019 Jan 3. PMID:30677741 doi:http://dx.doi.org/10.1016/j.isci.2018.12.030
