A monoclonal antibody 14F10 was raised against Golgi fractions from Sf21 cells and selected as Golgi specific. Immunohistochemical stainings with the antibody localized the antigen in Golgi cisterns of the cells. The antigen was purified and shown to be a 130-K membrane protein with N-glycans and intrachain disulfide bonds. Amino acid sequencing of its peptide fragments revealed that the antigen contained homologous sequences to those encoded by CG7190 and CG7193 Drosophila melanogaster genes. No possible transmembrane domain existed in these deduced amino acid sequences, while one did in that encoded by CG7195, an adjacent gene to CG7193. Furthermore, 5' and 3' expression sequence tags of LD19434 had been mapped to CG7190 and a downstream region of CG7195, respectively. These findings supported that all of these genes actually composed a single gene, which encoded an orthologous protein to a vertebrate Golgi-resident protein, Golgi apparatus protein 1, also called cysteine-rich FGF receptor, E-selectin ligand-1, or latent TGF-beta complex protein-1. Our results suggested that the Golgi apparatus protein 1 played a critical role in the Golgi cisterns through the animal kingdom.