Designed Trp-Cage Proteins with Antimicrobial Activity and Enhanced Stability.

α-Helical antimicrobial peptides (αAMPs) are among the potential candidates for new anti-infectives to tackle the global crisis in antibiotic resistance, but they suffer from low bioavailability due to high susceptibility to enzymatic degradation. Here, we describe a strategy to increase the resistance of αAMPs against proteases. Fusing the 12-residue αAMP KR-12 with a Trp-cage domain induces an α-helical structure in the otherwise unfolded KR-12 moiety in solution. The resulting antimicrobial Trp-cage exhibits higher proteolytic resistance due to its stable fold as evidenced by correlating sequence-resolved digest data with structural analyses. In addition, the antimicrobial Trp-cage displays increased activity against bacteria in the presence of physiologically relevant concentrations of NaCl, while the hemolytic activity remains negligible. In contrast to previous strategies, the presented approach is not reliant on artificial amino acids and is therefore applicable to biosynthetic procedures. Our study aims to improve the pharmacokinetics of αAMPs to facilitate their use as therapeutics.