Rational design of short antifreeze peptides derived from Rhagium inquisitor antifreeze protein

Abstract

Abstract Organisms living in an extremely cold environment utilize antifreeze proteins (AFPs) to inhibit ice formation and maintain their biochemical processes. AFPs are produced across various kingdoms including plants, microorganisms, and insects. In the present study, several short peptides were designed based on the ice-binding site of AFP found in a longhorn beetle, Rhagium inquisitor. Six peptides (RiAFP1–6) with different lengths ranging from 9 to 12 residues were designed based on the repetitive ice-binding TxTxTxT motif of its parent protein. All of the designed peptides displayed thermal hysteresis (TH) activity between 0.03–0.10 °C and ice recrystallization inhibition (IRI) activity between 0.17–1.04 μm2. Peptides RiAFP2 and RiAFP6 showed the highest TH activity (0.10 °C) while did not cause ice morphology changes. On the other hand, peptides RiAFP5 was the least active in terms of TH, yet this peptide caused significant ice morphology changes. Interestingly, IRI analysis showed that peptide RiAFP5 had the highest activity with an average ice crystal size of 0.17 μm2. Molecular dynamics (MD) simulation was carried out to observe the flexibility and dynamics of the designed peptides in water. Our MD results showed that peptide RiFAP5 was the least flexible peptide among the designed peptides, which presumably rendered its ice recrystallization inhibition activity.