Cystinosin

CTNS may also refer to the Center for Theology and the Natural Sciences.149783429ENSG00000040531ENSMUSG00000005949O60931P57757NM_001031681NM_004937NM_031251NM_001357891NM_001357892NP_001026851NP_004928NP_112541NP_001344820NP_001344821 CTNS may also refer to the Center for Theology and the Natural Sciences. CTNS is the gene that encodes the protein cystinosin in humans. Cystinosin is a lysosomal seven-transmembrane protein that functions as an active transporter for the export of cystine molecules out of the lysosome. Mutations in CTNS are responsible for cystinosis, an autosomal recessive lysosomal storage disease. In 1995, the gene was localized to the short arm of chromosome 17. An international collaborative effort finally succeeded in isolating CTNS by positional cloning in 1998. CTNS is located on the p arm of human chromosome 17, at position 13.2. It spans base pairs 3,636,468 and 3,661,542, and comprises 12 exons. The gene is expressed in the lysosomes of all organs and tissues. Cystinosin has also been found in melanosomes in melanocytes. Cystinosin is a seven-transmembrane domain receptor embedded in the lysosomal membrane, and is a member of the lysosomal cystine transporter family of transport proteins. It comprises 367 amino acid residues, and has a molecular mass of 41738 Da. Cystinosin has seven N-glycosylation sites in the N-terminus region, spanning a range of 128 amino acid residues. The receptor also has two sorting motifs; a GYDQL motif in the C-terminus region, and a YFPQA motif, known as the 'PQ loop,' on the fifth inter-transmembrane α-helix moiety. The protein obeys Michaelis-Menton kinetics and has an associated KM of 278 ± 49 µM.