Figure 5.

Protamines of M. polymorpha sperm are the post-translational cleavage products from three PL histone H1 precursors Pl-1, PL-2, and PL-3. a, amino acid sequences of the three PL precursors. The boxes with green borders indicate the WHD, which is characteristic of H1 histones. The regions underlined in yellow correspond to the peptides identified in mature sperm. The region of Pl-1 underlined in brown represents the first M. polymorpha protamine sequence determined using conventional Edman degradation sequencing (26). b, schematic representation of the post-translational cleavage undergone by M. polymorpha PLs. Precursor SNBP histone H1-related PLs consisting of an N-terminal (N) winged helix domain (WDH) and an arginine-rich C-terminal domain (C) are post-translationally cleaved (red arrows) into smaller fragments (yellow) and further C-terminally di-aminopropanelated (dark red dots). c, amino acid sequence of the protamines (Fig. 1a, lane 1) identified by MS. d, schematic representation of the intermediate liquid phase chromatin condensation stage observed in spermatids (Fig. 4).