Protamine
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Protamines are small, arginine-rich, nuclear proteins that replace histones late in the haploid phase of spermatogenesis and are believed essential for sperm head condensation and DNA stabilization. Mice, humans, and certain fish have 2 or more different protamines, whereas the sperm of bull, boar, rat, rabbit, guinea pig, and ram have one form of protamine. The 2 human protamines are denoted PRM1 and PRM2.
When mixed with insulin, protamines slow down the onset and duration of insulin action (see NPH insulin).
Examples of protamines from fish are:
- salmine from salmon
- clupeine from herring sperm (Clupea)
- iridine from rainbow trout
- thinnine from tunafish (Thunnus)
- stelline from starry sturgeon (Acipenser stellatus)
- scylliorhinine from dogfish (Scylliorhinus)
