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PDBsum entry 2py2
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Antifreeze protein
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PDB id
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2py2
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References listed in PDB file
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Key reference
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Title
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Structure and evolutionary origin of ca(2+)-Dependent herring type ii antifreeze protein.
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Authors
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Y.Liu,
Z.Li,
Q.Lin,
J.Kosinski,
J.Seetharaman,
J.M.Bujnicki,
J.Sivaraman,
C.L.Hew.
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Ref.
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Plos One, 2007,
2,
e548.
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PubMed id
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Abstract
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In order to survive under extremely cold environments, many organisms produce
antifreeze proteins (AFPs). AFPs inhibit the growth of ice crystals and protect
organisms from freezing damage. Fish AFPs can be classified into five distinct
types based on their structures. Here we report the structure of herring AFP
(hAFP), a Ca(2+)-dependent fish type II AFP. It exhibits a fold similar to the
C-type (Ca(2+)-dependent) lectins with unique ice-binding features. The 1.7 A
crystal structure of hAFP with bound Ca(2+) and site-directed mutagenesis reveal
an ice-binding site consisting of Thr96, Thr98 and Ca(2+)-coordinating residues
Asp94 and Glu99, which initiate hAFP adsorption onto the [10-10] prism plane of
the ice lattice. The hAFP-ice interaction is further strengthened by the bound
Ca(2+) through the coordination with a water molecule of the ice lattice. This
Ca(2+)-coordinated ice-binding mechanism is distinct from previously proposed
mechanisms for other AFPs. However, phylogenetic analysis suggests that all type
II AFPs evolved from the common ancestor and developed different ice-binding
modes. We clarify the evolutionary relationship of type II AFPs to sugar-binding
lectins.
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