Seminal plasma peptides inhibiting RNA synthesis

A peptide fraction, called seminal plasma inhibitor (SPI), present in mammalian semen, was shown to block DNA transcription in vitro (Lugaro et al., 1984). Peptides responsible for this effect were partially purified from bovine seminal plasma. This report outlines the preparative procedure for the isolation of SPI and provides preliminary information on the action mechanism of the RNA synthesis inhibition.