CLOSING, FUNCTIONAL EXPRESSION, AND CHROMOSOMAL LOCALIZATION OF THE HUMAN AND MOUSE GP180-CARBOXYPEPTIDASE D-LIKE ENZYME

We previously reported that a host cell glycoprotein, gp180, binds duc k hepatitis B virus particles, and is encoded by a member of the carbo xypeptidase gene family (Kuroki, K., Eng, F., Ishikawa, T., Turck, C., Harada, F., Ganem, D., 1995. gp180, a host cell glycoprotein that bin ds duck hepatitis B virus particles, is encoded by a member of the car boxypeptidase gene family. J. Biol. Chem. 270, 15022-15028). After tha t report, carboxypeptidase D (CPD) was subsequently purified from bovi ne pituitary and characterized as a novel carboxypeptidase E (CPE)-lik e enzyme, with many characteristics in common with duck gp180 (Song, L ., Fricker, L.D., 1995. Purification and characterization of carboxype ptidase D, a novel carboxypeptidase E-like enzyme, from bovine pituita ry. J. Biol. Chem. 270, 25007-25013). CPD is now supposed to play an i mportant role in a secretory pathway. To clarify the function of gp180 further, we have isolated and analyzed human and mouse homologues of duck gp180. cDNA clones derived from human HepG2 cells and mouse liver s have been isolated on the basis of homology to the duck gp180. The s uggested open reading frames of the human and mouse cDNA encode 1380 a nd 1377 amino acid proteins, respectively and have three carboxypeptid ase homologous domains (A, B, and C). Domains A and B have completely conserved the residues known to have the enzymatic activity of carboxy peptidase, but domain C in each cDNA does not. Northern blotting revea led a ubiquitous tissue distribution of human gp180 mRNA with several transcript species. Expression of human gp180 cDNA in transfected 293T cells exhibited carboxypeptidase activity upon radiometric assay. The human and mouse homologues of duck gp180 have many characteristics in common with bovine CPD. Fluorescence in-situ hybridization reveals th at the gene encoding human gp180 is located in region 17q11.2. (C) 199 8 Elsevier Science B.V. All rights reserved.