1hg7
From Proteopedia
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HIGH RESOLUTION STRUCTURE OF HPLC-12 TYPE III ANTIFREEZE PROTEIN FROM OCEAN POUT MACROZOARCES AMERICANUS
Overview
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.
About this Structure
1HG7 is a Single protein structure of sequence from Macrozoarces americanus with as ligand. Full crystallographic information is available from OCA.
Reference
Understanding the mechanism of ice binding by type III antifreeze proteins., Antson AA, Smith DJ, Roper DI, Lewis S, Caves LS, Verma CS, Buckley SL, Lillford PJ, Hubbard RE, J Mol Biol. 2001 Jan 26;305(4):875-89. PMID:11162099
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