Protamines substitute for histones in the chromatin of sperm during the haploid phase of spermatogenesis. They compact sperm DNA into a highly condensed, stable and inactive complex. Gonads. Phosphorylated in immature sperm. Dephosphorylated in mature sperm allowing a stronger interaction with DNA. Unphosphorylated. Two isoforms exist, a major form and a minor form. This is the minor form.