Transition protein 1 from boar late spermatid nuclei having DNA-melting activity is a dimeric protein

Polyacrylamide gel electrophoretic behavior of boar transition protein 1, TP1, under dissociating and non-dissociating buffer conditions, and titration of fluorescently labeled TP1 with increasing amounts of TP1 showed that TP1 formed a dimer without intermolecular disulfide bond. TP1 dimer with intermolecular disulfide bond had similar DNA-melting activity to TP1, but was not detected in extracts from boar late spermatid nuclei. These results suggest that TP1 dimer without intermolecular disulfide bond induces local destabilization of DNA in the late spermatid nuclei.