Solution structure of a mini IGF‐1

Abstract

Mini insulin-like growth factor 1, an inactive insulin-like growth factor I mutant lacking the C region, was studied by 2D NMR spectroscopy. Resonances were assigned for almost all protons of the 57 amino acid residues. The 3D structure of the protein was determined by distance geometry methods. Three helical segments; Ala 8-Cys 18, Gly 42-Phe 49, and Leu 54-Cys 61, were identified, corresponding to those present in wild-type insulin-like growth factor 1 and in single-chain insulin. Their relative orientation, however, was found to be changed. This change is connected with a displacement of the Phe 23-Tyr 24-Phe 25-Asn 26 P-strand-like segment, i.e., of aromatic side chains known to be important for receptor binding. Thus, deletion of the C region of IGF-1 results in a substantial tertiary structural rearrangement that accounts for the loss of receptor affinity.

The Different Folding Behavior of Insulin and Insulin-like Growth Factor 1 Is Mainly Controlled by Their B-Chain/Domain

“…The expression vectors of mini-IGF-1, Ins(A)/IGF-1(B), and Ins(B)/IGF-1(A) were respectively constructed as shown in Figure 2A. To obtain the mini-IGF-1 gene, four partially complementary DNA fragments were FIGURE 1: Strand models of (A) insulin [R state of crystal structure (2)], (B) mini-proinsulin [solution structure (8)], (C) swap insulin [solution structure (28)], (D) IGF-1 [solution structure (10)], and (E) mini-IGF-1 [solution structure (11)]. The disulfides were pointed in the molecules.…”

“…So, the insulin-like structure of IGF-1 is mainly encoded by its A-and B-domains. When B28Pro and A1Gly were directly connected by a peptide bond, the mini-IGF-1 still retained the three helical segments presented in the native IGF-1, but the relative orientation of the three helixes had been changed (11) (Figure 1E) and its biological activity has been lost completely.…”

Solution Structure and Backbone Dynamics of Long-[Arg3]insulin-like Growth Factor-I

“…Thus far, the only refined structures of proteins from the IGF family include two reports of the IGF-I structure, both obtained by homonuclear NMR techniques (9,10), two structures of IGF-II obtained by a combined homonuclear/heteronuclear NMR approach (13,14), and the structure of a mini-IGF-I, which has the C-domain deleted (15). Detailed analysis of the protein dynamics has not been reported for any of the IGF proteins.…”

“…Acknowledgments-We acknowledge Professor K. Wü thrich (ETH, Zü rich) for providing us with the XEASY, SPSCAN, MOLMOL, and DYANA software packages, Professor Lewis Kay (University of Toronto, Toronto) for providing us with the code for the sensitivityenhanced 15 N pulse sequences, and Dr. Peter Jeffrey (Australian National University) for assistance with the sedimentation equilibrium experiments and analysis. We also thank Dr. Christina Redfield for her advice and careful reading of the manuscript.…”

A note on comparison of exon 2 of the IGF-I gene in four species of the family <i>Canidae</i>

“…The insulin-like growth factor 1 is a small polypeptide (70-aminoacid), composed of three helical segments: helix I (Ala8-Cys 18), helix II (Gly 42-Phe 49) and helix III (Leu 54-Cys 61) (Wolf et al, 1996), which is structurally related to insulin. This protein plays a fundamental role in the regulation of the postnatal weight, metabolism and foetal development in mammals.…”