An edge β-strand mutation turns ubiquitin into a pore-forming amyloid

Ubiquitin (Ub) is a highly conserved eukaryotic protein, generally regarded as stable and soluble under physiological conditions, playing a key role in maintaining cellular protein balance. Using complementary bioinformatic, biophysical, immunochemical, and electrophysiological approaches, we show that a single point mutation—the substitution of Glu16 with Val (E16V) in an edge β-strand—dramatically alters Ub behavior, inducing amyloid-like aggregation, membrane permeabilization, and cytotoxicity. Remarkably, E16V retains the native globular fold of wild-type Ub in aqueous solution, yet undergoes a functional switch upon interaction with anionic membranes. E16V assembles into prefibrillar oligomers, forms voltage-dependent ion channels with well-defined conductance states and lifetimes, and disrupts membrane integrity in both bacterial and mammalian cells. In contrast, wildtype Ub remains monomeric and inert under identical conditions. Synthetic peptides encompassing the mutated β-strand reproduce the cytotoxic effects, supporting a localized, sequence-specific mechanism of action reminiscent of amyloidogenic motifs found in yeast adhesins. These findings uncover a hidden amyloidogenic potential in Ub and establish the E16V mutant as a unique model for membrane-triggered amyloid pore formation and the rational design of membrane-active antimicrobial peptides.