PURIFICATION AND CHARACTERIZATION OF THE FISH SEX-SPECIFIC TESTICULARPROTEIN

Male herring (Clupea harengus) and rainbow trout (Oncorhynchus mykiss) gonads have a high level of specific protein, which is absent in fema le gonads. This fish sex-specific testicular protein (FSSTP) appears a s a heavily stained band after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) which has a molecular weight of 43 kDa. The FSSTP was purified to homogeneity by ammonium sulphate fractionat ion, ion exchange chromatography on DEAE-Sepharose, affinity chromatog raphy on Red Agarose and gel filtration on Sephadex G-100. In both spe cies, the FSSTP has a molecular weight of about 75 kDa and is composed of two monomeric proteins when molecular weight is estimated under no n-denaturating conditions. The FSSTR has its isoelectric point at pH 5 .51. The protein shows a high content of aspartate/asparagine and glut mate/glutamine residues and trace amounts of cysteine. The glycine, le ucine and lysine content is markedly higher and the tyrosine is notice ably lower than the content of the remaining amino acids. The function and origin of this specific protein are discussed.