Ice-binding site of snow mold fungus antifreeze protein deviates from structural regularity and high conservation

摘要: Antifreeze proteins (AFPs) are found in organisms ranging from fish to bacteria, where they serve different functions facilitate survival of their host. AFPs that protect freeze-intolerant and insects internal ice growth bind using a regular array well-conserved residues/motifs. Less is known about the role freeze-tolerant species, which might be beneficially alter structure or around Here we report 0.95-A high-resolution crystal 223-residue secreted AFP snow mold fungus Typhula ishikariensis. Its main structural element an irregular β-helix with six loops 18 more residues lies alongside α-helix. β-Helices have independently evolved as on several occasions seem ideally structured planes ice, including basal plane. A novelty β-helical fold nonsequential arrangement places N- C termini inside solenoid coils. The ice-binding site (IBS), could not predicted sequence structure, was located by site-directed mutagenesis flattest surface protein. It remarkable for its lack regularity poor conservation homologs psychrophilic diatoms bacteria other fungi.