MELANOBLAST MELANOCYTE EARLY MARKER (MELEM) IS A GLUTATHIONE-S-TRANSFERASE SUBUNIT/

We have biochemically characterized the antigen recognized by the mela noblast/melanocyte early marker (MelEM) monoclonal antibody (Mab) whic h labels early melanoblasts and melanocytes in the avian embryo [1], W hile among the neural crest derivatives MelEM Mab is strictly specific for the melanocytic lineage, some endodermal derivatives such as hepa tocytes react with this Mab, Since MelEM Mab immunoprecitates a protei n of the same relative mass from both liver extracts and melanocytes, we immunopurified MelEM protein from liver extract of quail embryos at 10 days of incubation. The N-terminal sequence of this protein being blocked, we determined three internal peptide sequences, Our study rev eals that the MelEM protein is an Alpha class subunit of glutathione S -transferase which is common to hepatocytes and to neural crest-derive d pigment cells during their differentiation. (C) 1995 Academic Press, Inc.