Cationic Amino Acid Transporter 4 (CAT4)

Transport of cationic amino acids (CAA) in mammalian cells occurs by a system designated 'system y+.' The first human CAA transporter identified was SLC7A1. By searching an EST database with the deduced amino acid sequence of SLC7A1, Sperandeo et al. (1998) identified the novel gene SLC7A4. They isolated a full-length human placenta SLC7A4 cDNA which encoded a deduced 636-amino acid protein with a calculated molecular mass of 68,310 Da. The predicted SLC7A4 protein contains 13 transmembrane-spanning domains, 5 potential N-glycosylation sites, and 2 putative protein kinase C phosphorylation sites. SLC7A4 shares 38.5% amino acid sequence homology with SLC7A1 and 37.8% homology with SLC7A2 . Northern blot analysis detected an abundant 2.4-kb SLC7A4 transcript in human brain, testis, and placenta.