Protein Constituents of Spermatozoa 109 



nuclear proteins are simply due to the use of material containing 

 variable proportions of mature and immature spermatozoa. Sperma- 

 tocytic development is well known to be associated with characteris- 

 tic changes in the amino acid composition of the nuclear proteins. 

 Immature spermatozoa of salmon, for instance, obtained directly 

 from excised testes, contain a histone instead of the salmine. Simi- 

 larly, the testes of the mackerel yield on extraction with dilute 

 hydrochloric acid a histone, 'scombron', instead of the protamine 

 'scombrine'. This and similar observations, prompted Kossel (1928) 

 to acclaim the histones as 'intermediary stages' in the transformation 

 of complex proteins into protamines. 



77?^ non-basic nuclear proteins; karyogen and chromosomin 



In addition to the basic proteins, the sperm nucleus always con- 

 tains some non-basic or so-called residual proteins. In lipid-free 

 preparations from salmon sperm-heads, Miescher found 19-78% 

 protamine (extracted with 0-25-0-5% HCl), 2-94% acid-soluble pro- 

 tein material other than protamine, 60-50% of nucleic acid (ex- 

 tracted with NaOH) and 16-78% of an iron-containing residue 

 which was insoluble either in acid or in alkali and which he believed 

 to contain 'karyogen', the 'inner-space protein substance' {Innen- 

 raumsubstanz), of the sperm nucleus. 



It was found later that the residual or non-basic nuclear proteins, 

 unlike the protamines and histones, contain tryptophan as a 

 characteristic component. Opinions are divided, however, on the 

 problem of the actual ratio of non-basic to basic proteins in the 

 sperm nucleus. According to the Stedmans (1943, 1947), the nucleo- 

 protamine present in the sperm-heads of salmon accounts for no 

 more than 70% of the dry, lipid-free material, whereas the remainder 

 is made up largely of a non-basic protein 'chromosomin', which 

 contains tryptophan.* On the other hand, PoUister and Mirsky 

 (1946) state that the nucleoprotamine present in trout spermatozoa 



* The Stedmans' chromosomin must not be confused with chromosin, 

 a name given by Mirsky and Pollister (1946) to a complex extracted with 

 M-NaCl from isolated cell nuclei of various organs, including thymus, 

 liver, spleen, pancreas, brain, frog testes and bacteria. This complex 

 is composed of deoxyribonucleic acid, histone, and a tryptophan-contain- 

 ing protein. 



