Synthetic and structural studies on Pyrularia pubera thionin: a single‐residue mutation enhances activity against Gram‐negative bacteria

Abstract
The thionin from Pyrularia pubera (Pp‐TH), a 47‐residue peptide with four internal disulfide bonds, was efficiently produced by chemical synthesis. Its antimicrobial activity in vitro against several representative pathogens (EC50=0.3–3.0 μM) was identical to that of natural Pp‐TH. This peptide has a unique Asp32 instead of the consensus Arg found in other thionins of the same family. In order to evaluate the effect of this mutation, the Arg32 analogue (Pp‐TH(D32R)) was also synthesized and showed a significant increase in antibiotic activity against several Gram‐negative bacteria, whereas it retained the same activity against other pathogens. The overall structure of Pp‐TH(D32R) was maintained, though a slight decrease in the helical content of the peptide was observed.