Patent ID: 7332572

Claim:
An isolated protein which is a cell surface protein having an ability to mediate the transport of an amino acid into a cell and having an ability to mediate the incorporation of at least one amino acid selected from the group consisting of leucine (Leu), isoleucine (Ile), phenylalanine (Phe), methionine (Met), tyrosine (Tyr), tryptophan (Trp), valine (Val), histidine (His) and other neutral amino acids into the cell in an Na + -independent manner, wherein the cell surface protein has an amino acid sequence selected from a) to d); a) amino acid sequence represented by SEQ ID NO:2, b) amino acid sequence represented by SEQ ID NO:4, c) amino acid sequence represented by SEQ ID NO:2, wherein 1 to 20 amino acid residue(s) is (are) substituted, deleted or added, d) amino acid sequence represented by SEQ ID NO:4, wherein 1 to 20 amino acid residue(s) is (are) substituted, deleted or added.