The biosynthesis of protamine during spermatogenesis of the mouse: extraction, partial characterization, and site of synthesis

A highly basic, testis-specific, chromosomal protein (MP) can be extracted with acid from testis cells of the mouse, but not from mature spermatozoa. A similar protein (MP') can be isolated from spermatozoa if they are first disrupted with β-mercaptoethanol and urea. The two proteins (MP and MP') are identical as characterized by polyacrylamide gel electrophoresis, Bio-Gel P-10 chromatography, amino-acid analysis and equilibrium ultracentrifugation. They are presumably mouse protamine. Both measurements of the sedimentation velocities of testis cells which synthesize mouse protamine and of the activity of spermatozoa after a pulse label with radioactive arginine show that protamine is synthesized 19 days after the last meiotic S-phase, that is, at an advanced stage of spermiogenesis.