Mft52, an acid-bristle protein in the cytosol that delivers precursor proteins to yeast mitochondria

We have identified a novel protein, Mft52, in the cytosol of yeast cells, Mft52 has a two-domain structure that includes a receptor-like carboxyl-terminal ''acid-bristle'' domain, which binds basic, amphipathic mitochondrial targeting sequences, Native Mft52, purified from the cytosol of yeast cells, is found as a large particle eluting in the void volume of a Superose 6 gel filtration column, Fusion proteins, consisting of mitochondrial targeting sequences fused to nonmitochondrial passenger proteins, are targeted to mitochondria in wild type yeast cells, but defects in the gene encoding Mft52 drastically reduce the delivery of these proteins to the mitochondria, We propose that Mft52 is a subunit of a particle that is part of a system of targeting factors and molecular chaperones mediating the earliest stages of protein targeting to the mitochondria.