Amino acid composition of sperm histones in the house cricket Acheta domesticus.

Histones were isolated from late spermatids and spermatozoa of the house cricket Acheta domesticus, and the individual histone fractions were separated by electrophoresis on polyacrylamide-urea gels. The stained gels were cut so as to isolate the different histone fractions, and the amino acid compositions were determined using the technique of Houston (Houston, L.L.: Anal. Biochem. 44, 81-88 (1971). Five of the histones had amino acid compositions resembling those for the histones of calf thymus and were thus identified as fractions F1, F3, F2a2, F2b, and F2al. Another protein (SH) located exclusively in the late spermatids and spermatozoa was found to be basic and histone-like. It is a protein containing relatively high amounts of arginine (12.6%) and low amounts of lysine (7.6%), and, as a result, it has a low ratio of lysine-arginine (0.6). Other noteworthy features are its high contents of serine, glutamic acid, and glycine. It is arginine rich histone and in this regard resembles other such proteins, but it does contain unique features which distinguish it from all previously described histones.