Mitochondrial intermembrane chaperone that participates in the import and insertion of some multi-pass transmembrane proteins into the mitochondrial inner membrane. Also required for the transfer of beta-barrel precursors from the TOM complex to the sorting and assembly machinery (SAM complex) of the outer membrane. Acts as a chaperone-like protein that protects the hydrophobic precursors from aggregation and guide them through the mitochondrial intermembrane space. The tim-8-tim-13 complex mediates the import of some proteins while the predominant tim-9/tin-9.1-tim-10/tin-10 70 kDa complex mediates the import of much more proteins (By similarity). Heterohexamer; composed of 3 copies of tim-8/ddp-1 and 3 copies of tin-13/tim-13, named soluble 70 kDa complex. Associates with the TIM22 complex, whose core is composed of tim-22 (By similarity). The twin CX3C motif contains 4 conserved Cys residues that form 2 disulfide bonds in the mitochondrial intermembrane space. However, during the transit of tin-13/tim-13 from cytoplasm into mitochondrion, the Cys residues probably coordinate zinc, thereby preventing folding and allowing its transfer across mitochondrial outer membrane (By similarity). Belongs to the small Tim family.