Essential core component of the TIM22 complex, a complex that mediates the import and insertion of multi-pass transmembrane proteins, such as mitochondrial carrier family members, into the mitochondrial inner membrane. In the TIM22 complex, it constitutes the voltage-activated and signal-gated channel. Forms a twin-pore translocase that uses the membrane potential as external driving force in 2 voltage-dependent steps. Mediates the insertion of precursor proteins in a 3 step process. After the precursor is tethered to the translocase without losing energy from the Delta(psi), 2 energy-requiring steps are needed. First, Delta(psi) acts on the precursor protein and promotes its docking in the translocase complex. Then, Delta(psi) and an internal signal peptide together induce rapid gating transitions in one pore and closing of the other pore and drive membrane insertion to completion. Component of the TIM22 complex, whose core is composed of TIM18, TIM22 and TIM54, associated with the peripheral proteins MRS5/TIM12 and the 70 kDa heterohexamer composed of TIM9 and TIM10 (or TIM8 and TIM13). Import into inner membrane protein requires TOM20 function. Belongs to the Tim17/Tim22/Tim23 family.