Figure depicts the experimental concept. PFK amyloid fibrils adopt β-sheet organization, displaying the lysine side chains on the fibrils' surface (Figure ), mimicking the lysine-rich amphiphilic pattern of PSMα3, the functional bacterial amyloid recently shown to catalyze hydrolysis of β-lactams . As shown in Figure , hydrolytic breakup of the four-member β-lactam The fluorescence emission experiment depicted in Figure confirms that PFK adopts fibril organization. Specifically, Figure presents the fluorescence emission of the amyloid-reporting dye Amytracker-680 upon its incubation with PFK (0.2 mM) dissolved in aqueous solutions comprising different KCl concentrations. PFK folding to β-sheet-based fibril formation is highly sensitive to the ionic strength, which interferes with the electrostatic repulsion between the positively charge lysine residues . Specifically, shielding of the electrostatic repulsion permits stacking of the peptide-chains in a juxtaposed antiparallel cross-β conformation (Figure ) and consequent fibril formation . Figure demonstrates that above a KCl concentration of approximately 0.2 M, fluorescence of the dye rapidly increased, indicating fibrillation of the PFK peptide . Second derivative analysis of the fluorescence curve in Figure confirms that 0.2 M KCl is the threshold concentration for fibril formation (Figure ). The structure transformation of PFK at 0.2M KCl is further supported by circular dichroism (CD) spectral data (Figure ) indicating a polyproline type II -β-sheet transformation, and Fourier transform infrared (FTIR) spectroscopy (Figure ). The TEM image in the inset in Figure shows the abundant PFK amyloid-like fibrils assembled. It should be noted that above a critical assembly concentration of 2 mM, PFK displays a propensity to fibrillate even without salt present, due to the amphiphilic nature of the peptide .