By looking at the symmetry of residues around the inside of the cavity in the mitochondrial transporters, Alan Robinson, Catherine Overy and Edmund Kunji have proposed a mechanism for how these proteins may work.
The mechanism of transport by mitochondrial carriers based on analysis of symmetry.
Robinson, A. J., Overy, C. & Kunji, E. R. S. (2008)
Proc. Natl. Acad. Sci. U. S. A. 105, 17766 - 17771.