In vitro specific phosphorylation of the human seminal proteins

A condition for active phosphorylation of the human seminal proteins was achieved by addition of 0% triton X-100 which inhibited the active ATPase. Analysis of the phosphorylated products by SDS-PAGE revealed that the products at 3 min after ejaculation were consisted mainly of the 72K, 70K, and 50K which changed to 25K, 18K and 17.5K at 30 min. There was massive degradation of the seminal plasma proteins during the first 30 min after the ejaculation, resulting in a generation of smaller molecular weight proteins. Comparison of the protein staining pattern and the autoradiographic pattern suggested that the phosphorylation was protein specific and preferentially occurred on larger molecular weight proteins which were subsequently broken down to those of smaller molecular weight. The protein specific phosphorylation was further demonstrated by the result from a two dimensional gel electrophoresis. The specific phosphorylation suggests that side-chain modification of the seminal proteins may regulate a physiological function of the semen.