Crystal Structure and Mutational Analysis of Ca2+-Independent Type II Antifreeze Protein from Longsnout Poacher, Brachyopsis rostratus

摘要: Abstract We recently found that longsnout poacher (Brachyosis rostratus) produces a Ca2+-independent type II antifreeze protein (lpAFP) and succeeded in expressing recombinant lpAFP using Phichia pastoris. Here, we report, for the first time, X-ray crystal structure of at 1.34 A resolution. The displayed relatively planar surface, which encompasses two loop regions (Cys86–Lys89 Asn91–Cys97) short β-strand (Trp109–Leu112) with three unstructured segments (Gly57–Ile58, Ala103–Ala104, Pro113–His118). Electrostatic calculation surface showed was divided roughly into hydrophobic area (composed lacking secondary structure) hydrophilic loops β-strand). Site-directed mutation Ile58 Phe center decreased activity significantly, whereas Leu112 an intermediate between areas retained complete activity. In area, peptide-swap mutant 60% despite simultaneous mutations eight residues. conclude epicenter ice-binding site is region, centered by Ile58, surface. built model on basis lattice match ice constrained water oxygen atoms surrounding structure. has been docked to prism (2-1-10) plane, different from one determined AFP sea raven (11-21), appears explain results mutagenesis analysis.