Tom22′, an 8-kDa trans-site receptor in plants and protozoans, is a conserved feature of the TOM complex that appeared early in the evolution of eukaryotes

Abstract

One of the earliest events in the evolution of mitochondria was the development a means to translocate proteins made in the cytosol into the "protomitochondrion." How this was achieved remains uncertain, and the nature of the earliest version of the protein translocation machinery is not known. Comparative sequence analysis suggests three subunits, Tom40, Tom7, and Tom22 as common elements of the protein translocase in the mitochondrial outer membrane in diverse extant eukaryotes, Tom22, the 22-kDa subunit, plays a critical role in the function of this complex in fungi and animals, and we show that an 8-kDa subunit of the plant translocase is a truncated form of Tom22. It has a single transm..