Primary Structure of Scombrine γ, Protamine Isolated from Spotted Mackerel (Scomber australasicus)

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Spotted mackerel protamine, scombrine, was isolated from the sperm of a spotted mackerel (Scomber australasicus) by extraction with sulfuric acid and fractionated into one major (scombrine II) and one minor (scombrine I) components by chromatography on CM-Sephadex C-25. Scombrine II gave a single band, whereas scombrine I gave three bands upon PAGE. Scombrine II (scombrine γ) consists of 34 amino acid residues, and its sequence is: Pro-Arg-Arg-Arg-Arg-Arg-Ala-Ser-Arg-Pro-Val-Arg-Arg-Arg-Arg-Arg-Ala-Arg-Arg-Ser-Thr-Ala-Val-Arg-Arg-Arg-Arg-Arg-Val-Val-Arg-Arg-Arg-Arg. The ion spray mass spectrum shows that scombrine γ has a molecular mass of 4, 532.13 Da. The other minor component (scombrine I) is considered to be a mixture of degradation products of scombrine γ based on the results of PAGE and ion spray mass spectrometry. Scombrine γ has a similar sequence to sardaine Z2 from striped bonito except for two positions.