Abstract

Amyloids are highly ordered protein aggregates with an elongated architecture that is stabilized by a β-sheet structural core. Though classically associated to protein misfolding disorders, reports on novel functional roles of these proteins have increasingly emerged in the past of decade. Moreover, the recent discovery that amyloids formed with rationally designed small peptides can exhibit catalytic reactivity has opened up new opportunities in both biology and biotechnology. The observed activities require the binding of divalent metals, giving rise to active metal-amyloid complexes. Previous work from our group showed that the assembly into amyloids of a small peptide containing the catalytic sequence from a nucleotydiltransferase (SDIDVFI), producing an hydrolytic catalytic activity of this peptide in the amyloid state that is dependent of Mn2+, mimicking an ATPase-like enzyme. We performed a kinetic characterization of this activity using different substrates (ATP, CTP, UTP, GTP and dATP) in order to understand the specificity of the Mn2+-amyloid complex. Our results showed no significant differences on the kinetic parameters KM, Vmax,and kcat except for dATP that exhibited a fivefold increase on these constants. We also studied the contribution of the aspartate residues on the activity of peptide SDIDVFI by analyzing the ATPase-like activity of three mutants: SAIDVFI, SDIAVFI and SEIEVFI. The results showed a remarkable deviation on Km and Vmax values for peptide SDIAVFI, suggesting a significant role for the second aspartate on the observed ATPase-like activity. Overall, our results should contribute towards a systematic understanding of the emerging activity observed in these metal-amyloid complexes that will help for the design of future catalytic amyloids with biotechnological and biological applications.