Component of the TIM22 complex, a complex that mediates the import and insertion of multi-pass transmembrane proteins into the mitochondrial inner membrane. The TIM22 complex forms a twin-pore translocase that uses the membrane potential as external driving force (By similarity). Heterohexamer; composed of 3 copies of timm9 and 3 copies of timm10, named soluble 70 kDa complex. Associates directly with the TIM22 complex, whose core is composed of timm22. Interacts with the transmembrane regions of multi-pass transmembrane proteins in transit (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 timm9/timm10 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.