The TIM23 complex is primarily involved in:
Inner mitochondrial membrane protein import presequence pathway uses TIM23 complex distinct carrier TIM22. After crossing outer membrane Tom40 pore proteins bearing N-terminal positively charged amphipathic presequence arginine lysine hydroxylated recognized via Tim50 IMS receptor presequence groove interacting Tim23 channel. TIM23 complex comprises Tim23 voltage-gated aqueous channel C-terminal domain four transmembrane helices regulated Tim50, Tim17 paralog stabilizing pore, Tim21 bridging respiratory chain, Mgr2 gating Tim50. Driving forces two components: membrane potential Delta psi negative 180 mV inside electrostatically attracting positive presequence electrophoresis, ATP-dependent presequence associated motor PAM containing matrix Hsp70 mtHsp70 anchored Tim44 co-chaperone Pam16-Pam18 regulating ATPase pulling polypetide Brownian ratchet into matrix. Matrix-targeted proteins processed cleaved mitochondrial processing peptidase MPP removing targeting sequence. Inner membrane proteins lateral release via stop-transfer hydrophobic sorting or conservative sorting via Oxa1 after matrix import. TIM23 does not transport lipids recycle proteins mediate degradation lipid handled ERMES proteolysis LON m-AAA. Essential respiration biogenesis TIM23 mutations multi-system disease lactic acidosis mitochondrial encephalomyopathy and developmental delay.
Ref: Neupert & Herrmann, Annu Rev Biochem 2007: TIM23 imports proteins into mitochondrial matrix via motor.