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Structure of IGF1 and IGF2

المؤلف:  Norman, A. W., & Henry, H. L.

المصدر:  Hormones

الجزء والصفحة:  3rd edition , p373

2026-06-06

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The primary sequence of IGF1 is shown in Figure 1, in which the similarity of its structure to that of insulin is illustrated. Figure 2 shows the sequence of IGF-2 which has the same overall structure as IGF-1, but is 3 amino acids shorter than IGF-1. The two IGFs share nearly 70% amino acid identity and the same placement of disulfide bonds, but differ in their binding properties to the receptors that mediate their actions.

Fig1. Amino acid sequence of human insulin-like growth factor-1, IGF-1. The 70 amino acids in IGF-1 occur in four domains. From the N-terminus these are: B, pink; C, gray; A, blue; and D, yellow. Darker amino acids with white lettering are those that are identical in human pro-insulin. The A and B domains are homologous to the A and B chains of the insulin molecule and the C domain is the equivalent of the C-peptide in pro-insulin.

Fig2. Structure of IGF-2. The amino acid sequence of IGF-2 (insulin-like growth factor-2) is shown; see Figure 1 for the structure of IGF-1 which is compared to that of pro-insulin. Here the (blue) circles are those that are identical between IGF-1 and IGF-2. Yellow residues are those that differ between the two peptides. The distance between the N-terminal and the first disulfide bond is greater by 3 amino acids in IGF-2 than in IGF-1 and the distance between the second and third disulfide bonds is smaller by 4 amino acids. Finally, the C-terminal piece following the third disulfide bond is shorter by 2 amino acids in IGF-2 and the peptide overall is 67 amino acids compared to 70 in IGF-1.