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Insulin–Insulin-like Growth Factors Hybrids as Molecular Probes of Hormone:Receptor Binding Specificity
journal contribution
posted on 2016-05-12, 00:00 authored by Květoslava Křížková, Martina Chrudinová, Anna Povalová, Irena Selicharová, Michaela Collinsová, Václav Vaněk, Andrzej M. Brzozowski, Jiří Jiráček, Lenka ŽákováInsulin, insulin-like
growth factors 1 and 2 (IGF-1 and -2, respectively),
and their receptors (IR and IGF-1R) are the key elements of a complex
hormonal system that is essential for the development and functioning
of humans. The C and D domains of IGFs (absent in insulin) likely
play important roles in the differential binding of IGF-1 and -2 to
IGF-1R and to the isoforms of IR (IR-A and IR-B) and specific activation
of these receptors. Here, we attempted to probe the impact of IGF-1
and IGF-2 D domains (DI and DII, respectively)
and the IGF-2 C domain (CII) on the receptor specificity
of these hormones. For this, we made two types of insulin hybrid analogues:
(i) with the C-terminus of the insulin A chain extended by the amino
acids from the DI and DII domains and (ii) with
the C-terminus of the insulin B chain extended by some amino acids
derived from the CII domain. The receptor binding affinities
of these analogues and their receptor autophosphorylation potentials
were characterized. Our results indicate that the DI domain
has a more negative impact than the DII domain does on
binding to IR, and that the DI domain Pro-Leu-Lys residues
are important factors for a different IR-A versus IR-B binding affinity
of IGF-1. We also showed that the additions of amino acids that partially
“mimic” the CII domain, to the C-terminus
of the insulin B chain, change the binding and autophosphorylation
specificity of insulin in favor of the “metabolic” IR-B
isoform. This opens new venues for rational enhancement of insulin
IR-B specificity by modifications beyond the C-terminus of its B chain.