Figure 6.

Alignments of vertebrate IGF1 signal peptides. (A) Amino acid sequences of IGF1 signal peptides from eight terrestrial vertebrates, coelacanth, and human in single-letter code. Differences are indicated, identities are depicted by dots, and a dash indicates no residue. The # next to the chicken and turkey indicates that a shorter IGF1 signal peptide of 25 amino acids is encoded by an alternative transcript in these two avian species (see Figs. 1 and 2). (B) Amino acid sequences of IGF1 signal peptides from 11 ray-finned fish and lamprey in single-letter code. Differences are indicated, with identities depicted by dots. A dash indicates no residue. Blue text depicts amino acid identities between the chicken in (A) and the tetraodon in (B), and red text indicates differences. The asterisk in front of the cave fish heading denotes the presence of an alternate signal peptide with the following 17 extra N-terminal amino acids: MTSKNKLLFVAWRRPAG. (C) Cladogram of the IGF1 signal peptide in vertebrates. The numbers at the nodes indicate fractional differences, with 0 representing the highest levels of similarity. The length of each branch approximates the evolutionary distance. Note that the IGF1 signal peptide in the coelacanth is more similar to that of other fish than is the mature IGF1 and that the lamprey is the outgroup in both comparisons (see Fig. 5C)