Primary structures of sardaines Z1 and Z2, protamines isolated from striped bonito (Sarda orientalis)

Striped bonito protamine, sardaine, was isolated from the sperm of striped bonito (Sarda orientalis) by extraction with sulfuric acid followed by ion-exchange chromatography. The preparation gave a single band upon polyacrylamide gel electrophoresis. Sardaine consists of 34 amino acid residues, and its sequence is: Pro-Arg-Arg-Arg-Arg-Arg-Ser(Ala)-Ser-Arg-Pro-Val-Arg-Arg-Arg-Arg-Arg-Tyr -Arg- Arg-Ser-Thr-Ala-Ala-Arg-Arg-Arg-Arg-Arg-Val-Val-Arg-Arg-Arg-Arg. At position 7, serine (sardaine Z1) is partially replaced by alanine (sardaine Z2). The ion spray mass spectrum shows that sardaines Z1 and Z2 have molecular masses of 4,612.49 and 4,596.09 Da, respectively. The sequence of sardaine Z1 is 100% identical with that of thynnine Z2 from tuna fish (both fish belong to Scombridae, Perciformes).