Diisopropylfluorophosphate-interacting proteinases of nuclei of rat testis cells

Nuclei and chromatin of seminiferous epithelial cells of rat testis contain acid-extractable and non-extractable proteins which interact readily with [3H]DFP (diisopropylfluorophosphate). Proteinase activity is closely associated with these DFP-interacting proteins, and the proteinase activities are inhibited by DFP and PMSF. DFP-interacting proteins of testis chromatin increase greatly in amount at 26-32 days after birth when spermatids are appearing in increasing numbers. In nuclei separated by zonal centrifugation on sucrose gradients, the DFP-labeled proteins are highest in activity in the elongated spermatids at the stage in spermiogenesis at which histones are being replaced by testis-specific proteins and protamines. Electrophoresis in SDS-polyacrylamide gels reveals the presence of three species of DFP-interacting proteins in nuclei of seminiferous epithelial cells of the testis. The chromatin of epididymal spermatozoa of the rat contains three or four species of DFP-interacting proteins by SDS-polyacrylamide electrophoresis and some of these labeled proteins co-migrate with two of the three basic proteins which are observed during electrophoresis on polyacrylamide gels in Triton-urea.