Molecular cloning, tissue distribution, and chromosomal localization of human cationic amino acid transporter 2 (HCAT2).

Human cationic amino acid transporter 2 (HCAT2) was isolated from a human intestine cDNA library. The nucleotide sequence of the coding region predicts a 658-amino-acid protein with a calculated molecular weight of 71,669. As 91% of the residues are identical with those of the mouse cationic amino acid transporter 2 (MCAT2), HCAT2 seems to be a human counterpart of MCAT2. We found no isoform as was present in MCAT2. In Northern blot analysis, a single (9.0 kb) HCAT2 mRNA transcript was present in various human tissues. The highest level of expression was observed in skeletal muscle and the lowest level in the kidney. Hydropathy plots indicated that the translated protein is predicted to have 14 transmembrane domains with three potential N-glycosylation sites. Two patients with lysinuric protein intolerance (MIM No. 222700) were analyzed for HCAT2 cDNA but no mutation was detected. The HCAT2 gene was assigned to human chromosome 8p21.3-p22.