Investigation of alanine mutations affecting insulin-like growth factor (IGF) I binding to IGF binding proteins

Abstract

Binding properties of wild type (WT) and six single amino acid substituted variants (E3A, E9A, D12A, D20A, F23A, and E58A) of insulin-like growth factor I (IGF-I) were analyzed with respect to their binding details to IGF binding proteins (IGFBPs) by molecular dynamics (MD) simulations. The binding sites and binding interactions on IGF-I and IGFBPs are screened and compared with the static X-ray structure. Electrostatic interaction is the primary driving force of the interaction between IGF-I and IGFBPs. Mutation may cause the rearrangement of binding sites, however, the unfolding of protein induced by mutation is not obvious in this work. We also provide the detailed picture of binding factors. And the results show that, whether the unfolding of helix occurs or not, the Ala mutation will change the molecular atmosphere of the binding interface by the rearrangement of conformation, and further affects the binding residues and binding interactions.

Understanding Insulin Endocrinology in Decapod Crustacea: Molecular Modelling Characterization of an Insulin-Binding Protein and Insulin-Like Peptides in the Eastern Spiny Lobster, Sagmariasus verreauxi

“…It is only more recently that the role of electrostatic interactions has been established. Chen et al, (2014) [ 51 ], conducted computational alanine scanning of IGFI to select mutation hotspots in order to conduct comparative molecular dynamic simulations. Five of the six determined hotspots were negatively charged (three Glu(E) and two Asp(D)) and electrostatic interactions were determined to be the dominant driving force behind the IGF-IGFBP interaction [ 51 ].…”

“…Chen et al, (2014) [ 51 ], conducted computational alanine scanning of IGFI to select mutation hotspots in order to conduct comparative molecular dynamic simulations. Five of the six determined hotspots were negatively charged (three Glu(E) and two Asp(D)) and electrostatic interactions were determined to be the dominant driving force behind the IGF-IGFBP interaction [ 51 ]. These simulations are in strong support of our electrostatic potential surface analyses, which describe an electropositive (IGFBP) to electronegative (IGF) complementarity in vertebrates ( Figure 9 and Figure S4 ).…”

“…Indeed, this is a common problem in IGFBP structural studies. Although well aware of the interactive nature of the IGFBP_N’ and C’ domains in the mediation of binding affinity, the N’ insulin-binding domain remains the focus of structural and affinity studies, mainly due to the poor ability to solve the flexible linking domain [ 51 ]. Yet, as we are well aware of the synergistic function of the N’ and C’ domains in mediating affinity [ 3 , 6 ], we must strive to generate interaction studies of the entire protein [ 37 ] in order to gain accurate in silico quantification of IGFBP binding affinity across ligands.…”