Protamine

Protamines are small highly basic protein compounds (proteins ) which have been detected in the nucleus of the sperm cells of vertebrates. Especially from the protamines of some fishes of the drug protamine is made.

Protamines replace during sperm production ( spermatogenesis) in late haploid phase histones and enable a particularly dense packing of the genetic information. In somatic cells protamines do not occur. In humans, we know the variants of protamine -1 ( PRM1 ) and protamine -2 ( PRM2 ).

Examples of sperm occurring species of fish protamines are clupeine ( herring, Clupeidae ), salmine ( salmon, Salmonidae ) and Iridin (rainbow trout, Salmo irideus ). There are in each case peptide mixtures whose fractions are very similar and consist of about 30-35 amino acids per molecule ( corresponding to a relative molecular weight of approximately 5kDa ), much of which constitutes the basic L- arginine.

In other protamines come next as basic amino acids arginine and lysine and histidine ago. The isoelectric point is at pH 12-13.