text: The Tim9-Tim10 complex is made up of three Tim9 molecules and three Tim10 molecules. Each Tim9 and Tim10 subunit consists of 80-110 amino acid residues with four conserved cysteine residues that form two intramolecular disulfide bonds. Each subunit folds into a helix-loop-helix structure, with each loop forming a donut shape that comprises the upper face of the complex. The structure of the Tim9-Tim10 complex takes on the form of an α-propeller, with two helical blades radiating from a narrow central pore.