The complete amino acid sequence of growth hormone of an elasmobranch, the blue shark (Prionace glauca).

The complete amino acid sequence of growth hormone (GH) from a phylogenetically ancient fish, the blue shark (Prionace glauca), was determined. The shark GH isolated from pituitary glands by U. J. Lewis, R. N. P. Singh, B. K. Seavey, R. Lasker, and G. E. Pickford (1972, Fish. Bull. 70, 933-939) was purified by reversed-phase high-performance liquid chromatography. The hormone was reduced, carboxymethylated, and subsequently cleaved in turn with cyanogen bromide and Staphylococcus aureus protease. The intact protein was also cleaved with lysyl endopeptidase and o-iodosobenzoic acid. The resulting peptide fragments were separated by rpHPLC and submitted to sequence analysis by automated and manual Edman methods. The shark GH consists of 183 amino acid residues with a calculated molecular weight of 21,081. Sequence comparisons revealed that the elasmobranch GH is considerably more similar to tetrapod GHs (e.g., 68% identity with sea turtle GH, 63% with chicken GH, and 58% with ovine GH) than teleostean GHs (e.g., 38% identities with salmon GH and 42% with bonito GH) except for eel GH (61% identity), and substantiates the earlier finding derived from the immunochemical and biological studies (Hayashida and Lewis, 1978) that the primitive fish are less diverged from the main line of vertebrate evolution leading to the tetrapod than are the modern bony fish.