The cDNA expression libraries derived from a highly metastatic cell subline Anip-973 and from its parental cell line, low metastatic AGZY-83a were screened by monoclonal antibodies (MoAbs) seperately against these two cell lines. A positive clone (H₄-D) from the Anip-973 cDNA library was isolated and its nucleotide sequence was determined. This clone contained 978 bp with an open reading frame of 318 bp encoding a polypeptide consisting of 106 amino acids. The H₄-D cDNA sequence showed 85% homology with a human propionyI-CoA carboxylase ct-chain. In Western bloting analysis, the MoAb H₄ recognized 2 bands (15 KDa and 27 KDa) of Anip-973 cell membrane protein. The mRNA expression of H₄-D was higher in Anip-973 cells than that in AGZY-83a cells. The metastatic potential of Anip-973 cells was markedly decreased after being pretreated with MoAb H₄. The above findings indicated that H₄-D has a certain relationship with the metastatic phenotype of Anip-973 cells.