Molecular basis of ACE2 inhibition by the peptide DX600 revealed by computational and biophysical analysis

This study investigates the molecular mechanism of Angiotensin-Converting Enzyme 2 (ACE2) inhibition by the peptide DX600 using an integrated com- putational and biophysical approach. Small molecules and peptides have been explored as ACE2 antagonists, including MLN-4760 and the peptide DX600, but the molecular determinants underlying their inhibitory mecha- nisms remain incompletely understood. MLN-4760 is known to interact within the catalytic cleft of ACE2 thereby inducing structural changes in ACE2 causing the receptor to undergo a transition from opened to closed conformation. On the contrary, our molecular dynamics simulations reveal that DX600 binding stabilizes the receptor, dampening fluctuations of key residues such as to lock the receptor in an open conformation. This stabili- zation produces a more rigid ACE2 structure, consistent with steric hin- drance that may impede viral protein, for example, the SARS-CoV-2 spike protein, engagement. RMSF analysis, which quantifies local structural fluc- tuations at the residue level, confirms that DX600 reduces local residue mobility, highlighting a distinct mechanism from small-molecule inhibitors. These results provide a detailed molecular picture of peptide-mediated ACE2 inhibition and offer insights for the rational design of ACE2-targeted small molecule therapeutics.