JBC, Vol. 250, Issue 15, 5791-5800, Aug, 1975
Changes in nuclear proteins of rat testis cells separated by velocity sedimentation
R. D. Platz, S. R. Grimes, M. L. Meistrich and L. S. Hnilica
The technique of velocity sedimentation at unit gravity has been used to
separate rat testis cell suspensions into fractions enriched in particular
cell types. Changes in the nuclear proteins from the various fractions have
been characterized by polyacrylamide gel electrophoresis, and correlated
with the changing morphology of the nucleus during spermatogenesis. The
most striking alterations in both protein composition and nuclear
morphology occur during spermatid maturation as both histone and
non-histone proteins are replaced by highly basic, low molecular weight,
spermatidal proteins. This replacement process is accompanied by a
quantitative reduction in both histone and non-histone proteins. The
synthesis of at least three basic proteins has been identified with late
stage spermatids. One of these proteins is a highly basic sperm-specific
protein containing high levels of cyst(e)ine and arginine. A second protein
synthesized in late stage spermatids is lysine rich, while the third
protein contains cyst(e)ine and co-migrates with histone F2a1 on acid-urea
polyacrylamide gels. The changes in protein composition of rat testis
nuclei after irradiation or hypophysectomy reflect the resulting changes in
the cellular composition of the testis. After selective elimination of the
germinal cells by irradiation, the electrophoretic pattern of acid-soluble
proteins from the testis is very similar to that of somatic tissue. Thus,
the cellular specificity of nuclear proteins demonstrated here using cell
separation techniques is also apparent following treatments which
selectively alter the cellular composition of the testis.
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