cDNA cloning of rat mitochondrial cyclophilin

Human cyclophilin-3 (hCyp-3) cDNA was used to screen a rat skeletal muscle cDNA library which led to the isolation of a full-length cDNA encoding the rat homologue. The derived amino acid sequence showed 89.5% identity with the human sequence, with major differences being restricted to the mitochondrial targeting sequence. The N-terminal sequence of the purified rat liver mitochondrial cyclophilin (CyP-D) corresponded to that derived from the cDNA following 30 amino acids of targeting sequence. This confirms that hCyp-3 encodes mitochondrial matrix CyP (CyP-D), which plays a crucial role in the mitochondrial permeability transition. CyP-D mRNA of a single sized (1.5 kb) was shown by Northern blotting to be present in liver, heart, skeletal muscle and brain.