Structural insight into the mitochondrial protein import system

Mitochondrial functions rely on precise and efficient transport of 1000-1500 different mitochondrial proteins from the cytosol to appropriate mitochondrial subcompartments. Those mitochondrial protein transport processes are mediated by the dedicated mitochondrial protein import system comprised of translocators in the outer and inner mitochondrial membranes and soluble factors in the cytosol, intermembrane space, and matrix. In the last decade, high-resolution structures of many of the components of the mitochondrial protein import machineries have become available, which has significantly advanced our understanding of the molecular mechanisms of mitochondrial protein transport. Here we review the currently available high-resolution structures of the components of the mitochondrial protein import machineries that afford structural and mechanistic insight into how the mitochondrial import system works. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.