Localization of Zinc in a Dense Fiber-Connecting Piece Fraction of Rat Sperm Tails Chemically Analogous to Hair Keratin

The study examined the distribution of zinc in mature rat sperm, finding that over 90% of zinc was located in the tail, primarily in -S-S-crosslinked structures resistant to disintegration in SDS. Zinc was associated with -SH groups, and its concentration decreased in both the heads and tails during epididymal passage. In the sperm head, a minor fraction of zinc was also linked to -S-S-bonded structures. In isolated tails, over 75% of zinc was retained in a subfraction mainly composed of dense fibers. The protein mixture from these structures had a similar amino acid composition to wool and guinea pig hair, suggesting a possible common phylogenetic origin and similar zinc interactions during assembly.