The Baculovirus Expression Vector Produces a Single Isoelectric Variant of Galectin-3

Abstract

Galectin-3, an animal lectin known to be involved in pre-mRNA splicing (Agrwal et aI, 1993), has been found in phosphorylated and unphosphorylated forms. The unphosphorylated form occurs mainly in the nucleus, while the phosphorylated form is present mainly in the cytoplasm. Correspondingly, quiescent cells contain predominantly the phosphorylated, cytoplasmic form, while proliferating cells have mainly the unphosphorylated nuclear form. A bacterial expression vector has been engineered and proven to produce solely the unphosphorylated form (Agrwal et aI, 1993). In this study, a recently constructed baculovirus expression vector for galectin-3 (Voss, unpublished) was used to produce and isolate the protein, which was then analyzed by two-dimensional electrophoresis. Only one form of gal-3 was observed, and it is hoped that the eucaryotic machinery of the infected insect cells has resulted in a vector which produces solely the phosphorylated form. However, attempts to confirm this by dephosphorylation with alkaline phosphatase have been as yet inconclusive.