1hg7 image
Deposition Date 2000-12-13
Release Date 2001-01-31
Last Version Date 2023-12-13
Entry Detail
PDB ID:
1HG7
Title:
High resolution structure of HPLC-12 type III antifreeze protein from Ocean Pout Macrozoarces americanus
Biological Source:
Source Organism:
Host Organism:
Method Details:
Experimental Method:
Resolution:
1.15 Å
R-Value Free:
0.16
R-Value Observed:
0.12
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:HPLC-12 TYPE III ANTIFREEZE PROTEIN
Mutations:YES
Chain IDs:A
Chain Length:66
Number of Molecules:1
Biological Source:MACROZOARCES AMERICANUS
Ligand Molecules
Primary Citation
Understanding the Mechanism of Ice Binding by Type III Antifreeze Protein
J.Mol.Biol. 305 875 ? (2001)
PMID: 11162099 DOI: 10.1006/JMBI.2000.4336

Abstact

Type III antifreeze proteins (AFPs) are present in the body fluids of some polar fishes where they inhibit ice growth at subzero temperatures. Previous studies of the structure of type III AFP by NMR and X-ray identified a remarkably flat surface on the protein containing amino acids that were demonstrated to be important for interaction with ice by mutational studies. It was proposed that this protein surface binds onto the (1 0 [\bar 1] 0) plane of ice with the key amino acids interacting directly with the water molecules in the ice crystal. Here, we show that the mechanism of type III AFP interaction with ice crystals is more complex than that proposed previously. We report a high-resolution X-ray structure of type III AFP refined at 1.15 A resolution with individual anisotropic temperature factors. We report the results of ice-etching experiments that show a broad surface coverage, suggesting that type III AFP binds to a set of planes that are parallel with or inclined at a small angle to the crystallographic c-axis of the ice crystal. Our modelling studies, performed with the refined structure, confirm that type III AFP can make energetically favourable interactions with several ice surfaces.

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