Open AccessTwo salmon neuropeptides encoded by one brain cDNA are structurally related to members of the glucagon superfamily
Author(s) -
PARKER David B.,
COE Imogen R.,
DIXON Gordon H.,
SHERWOOD Nancy M.
Publication year - 1993
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1993.tb18051.x
Subject(s) - peptide sequence , peptide , amino acid , complementary dna , biochemistry , biology , vasoactive intestinal peptide , signal peptide , neuropeptide , monobasic acid , peptide hormone , pituitary adenylate cyclase activating peptide , chemistry , hormone , gene , receptor , polymer chemistry
A cDNA that codes for two peptides in the glucagon superfamily has been isolated from sockeye salmon brain. The first peptide is related to growth hormone‐releasing hormone (GHRH), which has high sequence similarity with PACAP‐related peptide. The second peptide is structurally related to vasoactive intestinal peptide, which is also related to a newly identified peptide in mannals, pituitary adenylate‐cyclase‐activating polypeptide (PACAP). The salmon precursor contains 173 amino acids and has dibasic and monobasic enzyme‐processing sites for cleavage of a 45‐amino‐acid GHRH‐like peptide with a free C‐terminus and a 38‐amino‐acid PACAP with an amidated C‐terminus. The salmon GHRH‐like peptide has 40% amino acid sequence identity with the human GHRH and 56% identity with human PACAP‐related peptide. The 38‐amino‐acid salmon PACAP is highly conserved (89–92% identity) with only three or four amino acid substitutions compared with the human, ovine and rat 38‐amino‐acid PACAP. Not previously reported for mammalian species, a short precursor coding for only one peptide exists in salmon in addition to the long precursor coding for two peptides. In the short precursor, the coding region for GHRH is deleted leaving the PACAP‐coding region in a correct reading frame. This provides one possible control mechanism for an increased expression of one peptide (PACAP) without the concomitant increase in the other peptide (GHRH) as occurs in a double‐peptide precursor. The importance of the 3′non‐translated region of the salmon GHRH/PACAP precursor in the regulation of translation is suggested by its 70% nucleotide sequence identity to the 3′ non‐translated region of the mammalian PACAP precursors. The structural organization of the salmon GHRH/PACAP precursor provides a possible evolutionary scheme for precursors that contain tandem peptides in the glucagon superfamily.