Ornithine Transporter 1, Mitochondrial (ORNT1)

ORNT1 transports ornithine across the inner mitochondrial membrane from the cytosol to the mitochondrial matrix. The protein is an essential component of the urea cycle, and functions in ammonium detoxification and biosynthesis of the amino acid arginine. Mutations in this gene result in hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. There is a pseudogene of this locus on the Y chromosome. The protein has 3 repeats of about 100 amino acids and each repeat has 2 predicted transmembrane alpha-helices separated by a hydrophilic segment. Northern blot analysis detected a 4.2-kb mRNA transcript in liver and pancreas, with little expression in all other tissues. In mice, the expressed protein localized to liver mitochondria and varied with changes in dietary protein.