Distinct patterns of activation-dependent changes in conformational mobility between ERK1 and ERK2

▶ Hydrogen-exchange mass spectrometry (HX-MS) measures protein conformational mobility. ▶ Inactive vs active forms of the MAP kinase, ERK1, are compared by HX-MS. ▶ Kinase activation affects conformational mobility differently in related MAP kinases. ▶ Interdomain closure is constrained prior to activation of ERK2, but not ERK1. ▶ MAP kinases have distinct mechanisms for activation via control of protein motions.