The mitochondrial protein translocase family, which is responsible for movement of nuclear encoded pre-proteins into mitochondria, is very complex with at least 19 components. These proteins include several chaperone proteins, four proteins of the outer membrane translocase (Tom) import receptor, five proteins of the Tom channel complex, five proteins of the inner membrane translocase (Tim) and three "motor" proteins. This family represents the Tom22 proteins [1]. The N terminal region of Tom22 has been shown to have chaperone-like activity, and the C terminal region faces the intermembrane face [2].

1: Protein translocase of the outer mitochondrial membrane: role of import receptors in the structural organization of the TOM complex. Model K, Prinz T, Ruiz T, Radermacher M, Krimmer T, Kuhlbrandt W, Pfanner N, Meisinger C; J Mol Biol 2002;316:657-666. PMID:11866524

2: Mitochondrial import receptors Tom20 and Tom22 have chaperone-like activity. Yano M, Terada K, Mori M; J Biol Chem. 2004;279:10808-10813. PMID:14699115