Lipocentric Non-Pore-Forming Membrane Depolarization Underlies the Antibacterial Activity of Ribosomal Protein S30

Ribosomal protein S30 (RS30) exhibits potent antimicrobial activity, yet its precise mechanism of action has remained unresolved. Here, we uncover a fundamentally distinct mechanism by which RS30 kills bacteria through lipocentric, non-pore-forming membrane depolarization. By integrating microbiological assays, thermodynamic measurements, and quasielastic neutron scattering, we demonstrate that RS30 selectively binds anionic, bacterial-mimetic membranes via electrostatic interactions and markedly suppresses lipid lateral diffusion. This restriction of membrane mobility may promote lipid rearrangements that generate transient defects sufficient to collapse the membrane potential without large-scale permeabilization. The striking dissociation between depolarization and lysis implies a lipocentric mechanism centered on modulation of membrane dynamics rather than peptide oligomerization or stable transmembrane pore formation. Importantly, RS30 exhibits negligible cytotoxicity toward mammalian cells, highlighting its exceptional selectivity. These findings identify RS30 as a nonlytic antimicrobial agent and provide a strategic framework for next-generation therapeutics and precision infection-imaging probes.