Within the minimum LOH region on chromosome 17p13.3 deleted in hepatocellular carcinoma, a novel human plasma membrane-associated gene, named CT120, was isolated from a human kidney cDNA library using electronical cloning and RACE. The novel gene CT120 consists of 2145bp and encodes a protein with 257 amino acids. Database search revealed that homologs of CT120 exist in different organisms from plant to animal kingdoms, which suggests that CT120 is a highly conserved gene during biological evolution. Different expression patterns of CT120 were observed in many different human normal tissues and in various human tumor cell lines. Transcript of CT120 was not detectable in normal lung tissue, but was abundant in SPC-A-1 (human epithelial-like lung adenocarcinoma) cell line, suggesting that CT120 may be involved in lung cancer development. Subcellular localization analysis showed that CT120 is a novel membrane-associated protein. CT120 can interact with SLC3A2 (member 2 of solute carrier family 3) and GGTL3B (isoform of gamma-glutamyltranspeptidase-like 3) in eukaryotic cells by yeast two-hybrid screen and co-immunoprecipitation assay, which suggested that CT120 may assume very essential physiological functions involved in amino acid transport and glutathione metabolism.