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Abstract

Background: Tim23 mediates protein translocation into mitochondria. Results: Tim23 binds to mitochondria-like membranes through a hydrophobic anchor at its N terminus, with cardiolipin enhancing the interaction. Conclusion: The intermembrane space domain of Tim23 can interact with both inner and outer mitochondria-like membranes. Significance: Tim23 provides the central element for formation of the translocation contact. Tim23 mediates protein translocation into mitochondria. Although inserted into the inner membrane, the dynamic association of its intermembrane space (IMS) domain with the outer membrane promotes protein import. However, little is known about the molecular basis of this interaction. Here, we demonstrate that the IMS domain of Tim23 tightly associates with both inner and outer mitochondrial membrane-like membranes through a hydrophobic anchor at its N terminus. The structure of membrane-bound Tim23(IMS) is highly dynamic, allowing recognition of both the incoming presequence and other translocase components at the translocation contact. Cardiolipin enhances Tim23 membrane attachment, suggesting that cardiolipin can influence preprotein import.