FIG. 1.

Selective extraction of histones from the sperm chromatin by 0.65 M NaCl treatment. This procedure has released most of the histones from the sperm chromatin, leaving the protamines still associated with the DNA. Lane 1 contains 1 μg of protein extracted from human sperm nuclei and consists primarily of histones with no detectable protamines. Lane 2 contains 3.0 μg of protein which remained associated with the sperm chromatin after extraction. The fraction consists mostly of protamines with a trace amount of histones. Lane 3 contains 1 μg of calf thymus histones for comparison with lane 1. Calf thymus histones are different from human sperm histones but are of comparable size. Lane 4 contains 1 μg of salmon sperm protamines for comparison with lane 2. Salmon sperm protamines are smaller (∼30 amino acids) than human protamines (∼50 amino acids). The pattern of fractionation of histones and protamines is similar to that reported by Gatewood et al. (Fig. 2 of reference 12).