Purification of an ovine, androgen-dependent epididymal protein. Evidence for a strong amino acid sequence homology with serum albumin.
An ovine, testosterone-dependent protein was purified from an extract of epididymides of orchidectomized-, testosterone-implanted rams by ethylene glycol precipitation, anion exchange chromatography, preparative non-denaturing PAGE at alkaline pH and gel filtration. The protein which had previously been named ovine prealbumin-epididymis-specific protein (oPES), migrated as a single band ahead of ovine serum albumin (oSA). A single component, with an apparent MW of 60 kDa, lower than that of oSA, was also observed in SDS-PAGE. oPES was cleaved after lysyl residues using endoproteinase Lys-C and the hydrolysate was fractionated in 2 steps by reverse-phase HPLC. Six oligopeptides were recovered and sequenced. They all displayed complete identity with regions of bovine serum albumin scattered in the two-third N-terminal part. However, in 2 of them, there was no complete identity with homologous parts of oSA. This indicates that oPES and oSA are probably encoded by different genes.