Fine Details of IGF-1R Activation, Inhibition, and Asymmetry Determined by Associated Hydrogen/Deuterium-Exchange and Peptide Mass Mapping

The structural features of the asymmetric activated states of the insulin receptor family are still poorly understood. We investigated hydrogen/deuterium (H/D)-exchange within the extracellular domain of the type-I insulin-like growth factor receptor (IGF-1R) in the absence and presence of IGF-1 (active state) and in the presence of antibody inhibitors (inactive state). Near complete coverage of the 210 kDa receptor sequence was obtained by mass mapping of proteolytically derived peptides at all H/D-exchange time points. The data provide details regarding solvent exposure and dynamics across the extracellular region as well as conformational changes induced by activation or inactivation. Multiple peptides, distant in structure, individually demonstrated two distinct H/D-exchange rates, suggesting that each of these peptides exists in two separate environments in IGF-1R. The dual-exchange behavior of these peptides was enhanced on ligand binding and eliminated on inhibitor binding, clearly associating these regions with active state asymmetry and enabling them to serve as reporters of receptor activity.