In vitro Specific Phosphorylation of the Human Seminal Proteins

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Abstract
A condition for active phosphorylation of the human seminal proteins was achieved by addition of 0.1% triton X-100 which inhibited the active ATPase. Analysis of the phosphorylated products by SDS-PAGE [sodium dodecyl sulfate-polyacrylamide gel electrophoresis] revealed that the products at 3 min after ejaculation 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 MW proteins. Comparison of the protein staining pattern and the autoradiographic pattern suggested that the phosphorylation was protein specific and preferentially occurred on larger MW proteins which were subsequently broken down to those of smaller MW. The protein specific phosphorylation was further demonstrated by the result from a 2-dimensional gel electrophoresis. The specific phosphorylation suggests that side-chain modification of the seminal proteins may regulate a physiological function of the semen.