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Issue 18, 2017
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Conformational and hydration properties modulate ice recognition by type I antifreeze protein and its mutants

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Abstract

The mechanism of ice recognition by antifreeze protein (AFP) is a topic of recent interest. Here, using equilibrium simulations and free energy calculations, we provide structural rationale to the observed experimental anomalies on type I AFP (wfAFP isoform HPLC6) and its mutants as well as probe the molecular origin of ice recognition by them. Our results clearly demonstrate that the interplay between the conformational and hydration properties dictates the ice binding ability of type I AFP and its mutants. We find that HPLC6 exists as a highly stable long helix which adsorbs on the ice surface through the ordered water cages around the CH3 group of threonine (THR) residues, rather than directly binding to the ice surface via threonine (THR) through hydrogen bonding. Upon mutating THR with serine (SER), the straight helix conformation of HPLC6 disappears and the most stable conformation is a kinked helix devoid of ice binding ability. Free energy calculations reveal that there is a dynamic equilibrium between straight and bent helical conformations in the case of a valine (VAL) mutant. The straight long helical form of the VAL mutant also has the ability to form an ordered water cage structure around the CH3 groups of the VAL residues and thereby efficiently adsorbs on an ice plane similar to the wild type AFP.

Graphical abstract: Conformational and hydration properties modulate ice recognition by type I antifreeze protein and its mutants

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Publication details

The article was received on 11 Jan 2017, accepted on 12 Apr 2017 and first published on 12 Apr 2017


Article type: Paper
DOI: 10.1039/C7CP00221A
Citation: Phys. Chem. Chem. Phys., 2017,19, 11678-11689
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    Conformational and hydration properties modulate ice recognition by type I antifreeze protein and its mutants

    S. Chakraborty and B. Jana, Phys. Chem. Chem. Phys., 2017, 19, 11678
    DOI: 10.1039/C7CP00221A

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