The morphology and structural features of self-aggregating hexapeptides with antibiofilm formation activity

Abstract

Though self-aggregating peptides all aggregate into fibrils, they have been found to exert different roles against microbes, and the reasons remain unknown. In this study, we aimed to screen more self-aggregating hexapeptides with the highest fibrillation abilities using combined computational simulation methods and to study their effects against microbes (antimicrobial effect and antibiofilm-formation effect). Thereafter, we further explored the structural features of the self-aggregating hexapeptides leading to the different functions. By combining the use of three amyloid prediction software packages, we screened out 25 hexapeptides. Among them, 12 hexapeptides had antibiofilm activities (7 were stable), which were named as antibiofilm self-aggregating hexapeptides (ASAPs), while the remaining 13 hexapeptides had no effects on microbes. The ASAPs aggregated into fibril agglutinating bacteria, with the fibrils mainly divided into two classical morphologies, namely “twisted filaments” and “flat striated ribbons”, while the non-ASAPs aggregated into long bundles composed of numerous nanofibrils, or into amorphous polymers. Secondary structure analysis showed that the ASAP fibrils had predominantly β-sheets, and almost had no α-helices. In conclusion, our study revealed that the two types of fibrils aggregated by self-aggregating hexapeptides, i.e., “twisted filaments” and “flat striated ribbons”, were correlated with the agglutination function and the subsequent antibiofilm-formation activity, revealing a structure-function relationship of self-aggregating peptides.