The TIM23 complex mediates import of mitochondrial presequence-containing proteins into the mitochondrial matrix or insertion into the inner membrane. Following translocation of proteins across the outer mitochondrial membrane by the TOM complex, presequence-containing proteins are passed to the TIM23 complex and transported across the inner membrane. This requires the ATPase-activity of the matrix subcomplex, the presequence translocase-associated motor (PAM). A variation of the TIM23 complex, TIM23 SORT, lacks the PAM subcomplex and is instead associated with the TIM21. TIM23 SORT mediates the lateral insertion of protein precursors into the inner mitochondrial membrane. Lateral insertion is independent of ATP-hydrolysis and dependent on membrane potential. (Adapted from PMID:32074073,PMID:38828998 and PMID:19884344.)