Fig 1.
Comparison of insulin, IGF1 and IGF2 structure.
(A) Sequence alignment of insulin, IGF1 and IGF2. Different protein regions are indicated at the top. (B) Comparison of folded structure of insulin (blue), IGF1 (green) and IGF2 (gray).
Table 1.
Ligand affinities to IR-A and IR-B.
Fig 2.
Position 718 is important for low IGF1 affinity to IR-B without influencing insulin affinity.
IC50 values for insulin and IGF1 to WT IR-A and WT and exon 11 point-mutated IR-B midi receptors obtained in SPA binding assay with displacement of 125I-insulin for n = 3–4 independent experiments. *) Significant difference (p < 0.05) determined by ANOVA with Dunnet’s correction test.
Table 2.
IC50 (pM) of insulin and IGF1 to exon 11 point-mutated IR-B midi receptors.
Fig 3.
Displacement curves of 125I-insulin from WT IR and IR 718 mutants.
A representative binding curve for WT IR-A, IR-A P718A, IR-A P718E and IR-A P718K and WT IR-B, IR-B K718A, IR-B K718E and IR-B K718P displacement of 125I-insulin with insulin (●) or IGF2 (■) is shown. Each point is the mean with SEM of triplicates. The experiments were performed three to five independent times.
Table 3.
IC50 (pM) of insulin, IGF1 and IGF2 to position 718 mutated full length receptors.
Fig 4.
A representative IR activation curve of IR tyrosine phosphorylation measured in sandwich ELISA after stimulation with insulin (●), IGF1 (■) or IGF2 (▲) in full concentration-response curves. Each data point is three measurements with SEM. The experiments were performed three independent times.
Table 4.
EC50 values (nM) for IR activation and relative activation compared to IR-B.