Figure 2

Amino acid sequence conservation of vertebrate secretin family mature peptides. The mature peptide sequences were extracted by comparison with the human homologues and only the amino acid (aa) residues 1 to 27 are represented with the exception of the first 5 residues of human GLP1 (P01275). Takifugu GHRH was obtained from [93] (N000079, Assembly_4) and the lamprey GLP2 sequence for proglucagon II was not used since it was found to share very little similarity with other vertebrate members suggesting it has undergone species-specific evolution. Vertebrate peptides are grouped according to their potential origin from a PACAP-like exon or GCG-like exon. Percentage of identity (%ID) for the human homologue is given and the consensus sequences for each peptide group were deduced using the GeneDoc programme [90] and used to generate a PACAP-like and GCG-like subfamily peptide. The most frequent residues within the different peptide groups are annotated in bold and a prototype model sequence for the chordate secretin family members was derived by fusing the conserved PACAP-like and GCG-like subfamily amino acid sequence (overlapping residues are annotated in bold and italics). Accession numbers of the teleost and non-mammalian sequences used are indicated in Table 2. The human precursors are PHM/VIP, P01282; PRP/PACAP, P18509; GHRH, P01286; GCG/GLPs, P01275; GIP, P09681; and SCT, P09683 and mouse (Mus musculus) accession numbers are PHM/VIP, P32648; PRP/PACAP, O70176; GHRH, P16043; GCG/GLPs, P55095; GIP, P48756; and SCT, Q08535.