Conformational Changes and Energetic Analysis of the Open and Closed States of the M2-1 Protein of hRSV and hMPV Viruses

The Pneumoviridae family includes human Respiratory Syncytial Virus (hRSV) and human Metapneumovirus (hMPV), major causes of acute respiratory infections such as pneumonia and bronchiolitis in children worldwide. They also significantly impact respiratory morbidity in the elderly, immunocompromised individuals, and those with cardiopulmonary diseases. A key protein in their genome is M2-1, essential for viral genome transcription, replication, and modulation of the host immune response. Despite similar three-dimensional structures, the crystal structure of hMPV M2-1 tetramer reveals an asymmetric unit with one protomer adopting an open conformation, contrasting with hRSV M2-1's crystal structure. This asymmetry suggests dynamic equilibrium between open and closed states, aligning with M2-1's multifaceted roles in the viral system, tailored to specific functions. In this study, we modeled and constructed an equiprobable potential of M2-1 to capture conformational transitions between open and closed states. This robust approach captures thermodynamic properties, adjusting the potential to study transitions between different conformations. Starting from the open conformation, we observed conformational transitions to the closed state, enabling detailed analyses such as evaluating energy barriers, identifying key residues and regions involved, and highlighting major energetic differences between hMPV and hRSV. Energy perturbations in these regions allowed us to discuss transition mechanisms, including post-translational changes like phosphorylations. We also highlighted structural differences related to primary sequence variations, enabling analysis of local secondary structure effects. Future steps involve understanding the role of experimentally identified interactions in transitions, along with ligand design to directly influence conformational changes.