Protamine

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.

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Function

When mixed with insulin, protamines slow down the onset and increase the duration of insulin action (see NPH insulin).

Protamine sulfate is an antidote for heparin.^[1]

Examples

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.

Human

The 2 human protamines are denoted PRM1 and PRM2.

Fish

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)

References

1. ^ Byun Y, Chang LC, Lee LM, Han IS, Singh VK, Yang VC (2000). "Low molecular weight protamine: a potent but nontoxic antagonist to heparin/low molecular weight protamine". ASAIO J. 46 (4): 435–9. PMID 10926141.