After LETM1 was identified in a genomic Drosophila RNAi screen for mitochondrial Ca+/H+ exchanger (CHX), it has been suggested to catalyze the exchange of Ca2+ against H+ in both directions in a ruthenium red-sensitive pattern,70 which is difficult to reconcile with the CHX, and has been implicated in the pathogenesis of Parkinson’s disease through interaction with PINK1 (PTEN-induced kinase 1 [MIM: 608309]).71 Here, PINK1 is linked to Parkinson disease.