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, wild-type 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.