Testis Expressed Protein 4 (TEX4)

The Tim22 complex is a twin-pore translocase that mediates the insertion of precursor proteins in a 3-step process. After the precursor is tethered to the translocase without using energy from the membrane potential, 2 energy-requiring steps were needed. First, membrane potential acted on the precursor protein and promoted its docking in the translocase complex. Then, the membrane potential and an internal signal peptide together induced rapid gating transitions in one pore and closing of the other pore and drove membrane insertion to completion. Thus, protein insertion was driven by the coordinated action of a twin-pore complex in 2 voltage-dependent steps.Reconstituted Tim22 formed a hydrophilic, high-conductance channel with distinct opening states and pore diameters.