Protamines

PROTAMINES, proteins of a strongly basic character and alkaline reaction, found in combination with nucleic acids in fish sperm (Miescher) and studied in detail by Kossel. The preparation of protamines is based on their property as basic bodies to form salts with acids, for example, with sulfuric acid. The protamine from salmon milt (Salmo salar), salmine, forms a sulfate with the composition C₃₀H₅₇N₁₇O₆·2H₂SO₄·H₂O, and a chloroplatinate C₃₀H₅₇N₁₇O₆·4HCl·2PtCl₄; the protamine of herring (Clupea harengus), clupeine, has the composition C₃₀H₅₇N₁₇O₆; the composition of sturine from the sturgeon (Acipenser sturio) is C₃₃H₆₁N₁₇O₇ or possibly C₃₆H₆₉N₁₉O₇, and that of scombrine from the mackerel (Scomber scombrus) is C₃₀H₆₀N₁₆O₆. Nitrates, chlorides, and carbonates of protamines are easily soluble in water, sulfates are less so, and chromates are insoluble. Salmine sulfate diffuses through parchment, while clupeine sulfate does not diffuse. Protamines are rich in nitrogen (up to 30%), but apparently do not contain weakly bound (amide) nitrogen, nor do they contain sulfur. The amino acid composition of protamines is characterized by a richness in diamino acids (even more than 80%). The structure of protamines can be represented as polypeptides, polyarginides; a diarginide, for example, represents a compound of 2 molecules of arginine with 1 molecule of a monoamino acid: COOH | -NH CH CONH

HN :C-NH-C-NH₂

C : NH

NH

!

II NH

NH

(CH₂)₃ NH

I

or

i

>N-CH

C : NH

II II -HN CH CO- CO-------NH f NH₃ Protamines do not coagulate upon heating, are not split by pepsin and arginase, but are split under the influence of trypsin, erepsin, diluted acids, or alkalis, with the first products of splitting being protons, which are similar to peptones. Kossel classifies all protamines according to the number of diamino acids they contain: 1) monoprotamines, with one diamino acid—arginine (salmine, clupeine, scombrine, cyclopterine, etc.); 2) diprotamines, with two different diamino acids—arginine and histidine (percine), arginine and lysine (cyprinine, crepilabrine); 3) triprotamines, with three diamino acids—arginine, lysine, and histidine (sturine). Protamines can be considered as the simplest proteins, representing a transition to histones (see) and formed at the expense of muscle tissue proteins: Miescher showed that during the migration of salmon from seawater to fresh water for spawning, a sharp breakdown of musculature occurs along with an increase in the weight of the gonads; protamines are formed from the products of protein breakdown, and in immature testes, instead of protamines, histones are contained, also in combination with nucleic acids (Kossel).