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

Abstract

Abstract 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.