IF3 is also known as MTIF3 (mitochondrial translational initiation factor 3), DC38, IF3(mt) or IF-3mt, and is a 278 amino acid protein that is localized to mitochondria. IF3 aids in the initiation of protein synthesis by binding the 28S ribosomal subunit, which is a protein synthesis initiation site. The 28S and 39S ribosomal structures are subunits of the 55S ribosome, whose formation is favored in the absence of IF3, because IF3 allows the subunits to remain in their free form. Altered forms of IF3 may affect IF3’s function, which could alter the availability of mitochondrial encoded proteins, leading to oxidative stress and possibly causing an increased susceptibility to Parkinson’s disease. Polymorphism of the gene encoding IF3 is thought to be associated with Parkinson’s disease.