Abstract
Allosteric regulation represents a fundamental mechanism by which enzyme activity is modulated through distal binding events, yet the dynamic pathways that facilitate this communication often remain elusive to static structural methods. Hydrogen-deuterium exchange mass spectrometry (HDX-MS) has emerged as a premier technique for mapping these conformational transitions and protein dynamics in solution. This study investigates the allosteric activation pathways of a model kinase system, utilizing HDX-MS to identify regions of altered solvent accessibility and hydrogen bonding strength upon ligand binding and phosphorylation. By integrating bottom-up proteolysis with high-resolution mass spectrometry, we mapped the propagation of conformational signals from regulatory domains to the catalytic core. Our results reveal that allosteric activation is not merely a transition between two static states but involves a significant redistribution of the ensemble of conformational substates. Specifically, we identified a conserved network of hydrophobic residues and dynamic loops that undergo synchronized stabilization, facilitating the transition to an active conformation. Comparison with existing crystallographic data suggests that HDX-MS captures transient intermediate states that are critical for understanding the kinetic landscape of enzyme activation. These findings provide a detailed roadmap of allosteric communication, highlighting the utility of HDX-MS in drug discovery and the design of allosteric modulators. The methodology described herein offers a robust framework for dissecting the complex regulatory mechanisms of modular proteins, contributing to our broader understanding of molecular proteomics and structural biology as of early 2024.