Amino Acid Sequence of Eel Calcitonin

Abstract

The primary structure of eel calcitonin, containing 32 amino acid resudues, was elucidated using the reduced and aminoethylated derivative. Manual Edman degradation was employed from the N-terminus to the 31st residue in an average yield of about 90% and the C-terminal prolineamide was characterized as its dansyl derivative. The following amino acid sequence was deduced for eel calcitonin: Cys-Ser-Asn-Leu-Ser-Thr-Cys-Val-Leu-Gly-Lys-Leu-Ser-Gln-Glu-Leu-His-Lys-Leu-Gln-Thr-Tyr-Pro-Arg-Thr-Asp-Val-Gly-Ala-Gly-Thr-Pro-NH₂. Among the 32 amino acids of eel calcitonin only three amino acid replacements were observed, at the 26th, 27th, and 29th positions, in comparison with salmon calcitonin I, which is known to possess the highest hormonal activity among calcitonins so far isolated from various sources in a homogeneous state.