Printed in Sweden Copyright 0 1978 by Academic Preu, Inc. All rights of reproduction in any form reaerved 0014-4827/7X/1172-0347$02.00/O Experimental Cell Research 117 (1978) 347-356 BASIC NUCLEAR PROTEINS IN TESTICULAR CELLS AND EJACULATED SPERMATOZOA IN MAN N. TANPHAICHITR,’ P. SOBHON,2 N. TALUPPETH’ and P. CHALERMISARACHAP ‘Department of Biochemistry and 2Department of Anatomy, Faculty of Science, Mahidol University, Bangkok, Thailand SUMMARY Human testis was shown to contain a specific histone, TH2B, having the same electrophoretic mobility as rat TH2B. Testicular and ejaculated human sperm still possessed histones at 50 % and 15% of the total basic nuclear proteins, respectively. Comparison of the electrophoretic patterns of histones from human testis, testicular sperm and ejaculated sperm implied that the histones may be removed in the order H2A and Hl before H3, H4 and H2B before THZB. THZB which is the major hfstone fraction in ejaculated sperm has no longer a strong affinity to DNA. TH2B in sperm nuclei could be separated from other basic nuclear proteins by Bio-Gel P-IO column chromatography and its amino acid composition is similar to that of rat TH2B, although no cysteine residue was found. Several complicated intracellular events oc- cur during spermatogenesis and sperm maturation in mammalian testis and epidi- dymis. There is an increase in the chromo- somal condensation in sperm nucleus which stabilizes DNA during transport of sperm from the testis into the cervical tract. Con- comitant with this change, histones, basic nuclear proteins of a molecular weight of 11000-20 000, are also replaced by prota- mines, basic nuclear proteins rich in ar- ginine but of much lower molecular weight (around 5 000-7000) [l-3]. The amount of protamines in the nuclei has been corre- lated with the degree of chromosome con- densation [3], and is considered to be in- timately involved in this process. Unlike histones, protamines are more heterogeneous and vary from species to species [3,4,5]. Previously we have shown that protamines are more heterogeneous in humans than in other animals. There are three main fractions, HPl, HP2, HP3 and two minor fractions, HPSl and HPS2 [6]. Analysis of the amino acid compositions in- dicates high arginine content [7]; however, unlike other mammals, human protamines are also rich in glutamic acid (7.0 mol%) and histidine (9.8 mol%) [7]. Also two other testis specific histones, THl and TH2B, have been described [8,9, lo] with amino acid compositions similar to Hl and H2B. However, TH 1 and TH2B of rat and mouse have a higher acidic : basic amino acid ratio resulting in a slower elec- trophoretic mobility than Hl and H2B in acid-urea gels [8, 9, lo]. TH2B has also been shown to contain one cysteine. This amino acid was found only for l-2 residues in H3, but at a considerably higher level in mammalian protamines [ll]. In rats, the testis specific histones first appear in the primary spermatocytes and their amounts increase when the germ cells reach the spermatid stages [lo, 12, 131. These results imply that the testis specific histones may Exp Cell Res 117 (1978)