Intense myristoylation of a single protein in the ocular lens

A single protein of the ocular lens was intensely myristoylated following s hort term incubation of cultured bovine lens epithelial cells and intact ra t lenses with H-3-myristic acid. It was acidic (pI <5), about 19 kDa and pr esent exclusively in the cytosol of both cultured epithelial cells and the epithelium of the young rat lens. Fiber cell proteins were not labeled. The myristoylated protein was not seen in the epithelium of the adult rat. Ess entially no protein mass was evident in the 19-20 kDa range when samples of the labeled-soluble protein were fractionated by either HPLC coupled with SDS-PAGE-or 2D-electrophoresis. These findings suggest that the myristoylat ed-soluble protein-of 19 kDa in lens (p19(L)) is a rapidly-turning over min or protein likely associated with lens growth. The absence of any apparent membrane association for a myristoylated protein appears unusual. The trace nature of p19(L) has frustrated attempts at its identification by MALDI-MS . (C) 1999 Academic Press.