Mutant huntingtin inhibits mitochondrial protein import. Shown are cytosolic
compartment, mitochondrial inner and outer membranes, intermembrane space and
mitochondrial matrix. Mitochondrial preproteins translocate through the TOM
complex in the outer membrane. Matrix and many inner membrane and intermembrane
proteins are recognized by TIM23 subunits and translocate through the TIM23
complex. Mutant huntingtin full-length protein or mutant huntingtin N-terminal
peptide, both containing long polyglutamine (polyQ) repeat sequences, bind the
TIM23 complex, inhibiting protein import.