Isolation of the predominant coagulum protein of human semen before liquefaction

The predominant protein of freshly ejaculated human semen and seminal coagulum in reducing sodium dodecyl sulphate polyacrylamide gel electrophoresis was purified for the first time prior to cleavage of coagulum proteins during liquefaction. The method involves three steps using semen immediately after ejaculation. Washed seminal coagulum was first collected from fresh semen samples in acetate buffer at pH 4.5 at 0 degrees C, solubilized immediately in deionized urea followed by reduction and carboxymethylation of disulphide bonds among the aggregating coagulum proteins. Then using cation exchange (CM-Sephadex) chromatography, eluted with stepwise ionic strength gradient and finally Sephacryl S-300 high resolution chromatography in the presence of urea, the predominant coagulum protein was highly purified (99%) with a yield of 6.3%. The mol. wt of the purified protein was 57,000 Da. At physiological pH, the protein is rich in positive charge.