Determination of the Minimal Sequence Required for Antifreeze Activity of Type I Antifreeze Protein (AFP37)

Abstract

In order to elucidate the minimal sequence required for antifreeze activity of AFP 37, we synthesized a series of N- and C-terminal truncated peptides of AFP 37 with the central two Thr residues (Thr-13 and Thr-24) (Table 1). These truncated peptides (AFP 34, AFP 32, AFP 30, AFP 28, AFP 26, AFP 24, AFP 22 and AFP 20) were synthesized by a stepwise deletion of one residue or two residues from N- and C-terminus of AFP 37. Table 2 summarizes the thermal hysteresis values obtained with a series of truncated peptides of AFP 37. AFP 37, AFP 34, AFP 32, AFP 30 and AFP 28 show a linear dependence of the antifreeze activity on the concentrations of the peptides. AFP 34, AFP 32, AFP 30 and AFP 28 preserved 99.1%, 62.6%,56.16% and 15.9%thermal hysteresis activity of the wild type AFP (AFP 37) at a peptide concentration of 40 mg/mL, respectively. However, a significant hysteresis was not observed with any of the AFP 26, AFP24, AFP22 and AFP 20 at 40 mg/mL (data not shown). These results suggested that the minimalsequence required for antifreeze activity is from residue 5 toresidue 32 of AFP 37 (AFP 28).