Graves disease carrier protein (SLC25A16), associated with the inner mitochondrial membrane, mediates the transport of cytosolic coenzyme A (CoA-SH) into the mitochondrial matrix. Evidence for this event is indirect. The protein has the sequence motifs expected for a transport protein, and yeast cells deficient in its homologue, Leu5p, fail to accumulate mitochondrial CoA-SH and can be rescued by expression of SLC25A16. At the same time, neither the yeast nor the human protein has been shown directly to function as a transporter (Prohl et al. 2001, Leonardi et al. 2007).