As inferred from the yeast TIM9:TIM10 complex, the human TIMM9:TIMM10:FXC1 complex chaperones hydrophobic membrane proteins in the intermembrane space until their insertion into the inner or outer membrane. Whereas the yeast TIM9:TIM10 complex is soluble in the intermembrane space, the human TIMM9:TIMM10 complex is associated with the outer surface of the inner membrane (Muhlebein et al. 2004).
Experimentally verified substrates of the yeast TIM9:TIM10 complex include AAC (ADP/ATP translocase 1, ANT, SLC25A4 in human), TIM17 (TIMM17 in human), TOM40 (TOMM40 in human), TIM23 (TIMM23 in human), TIM22 (TIMM22 in human), and Tafazzin (Tafazzin, TAZ in human). Many other mitochondrial proteins are anticipated to be chaperoned by the TIMM9:TIMM10 complex.