Antifreeze Protein from Freeze-Tolerant Grass Has a Beta-Roll Fold with an Irregularly Structured Ice-Binding Site

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• 作者：Adam J. Middleton¹ ; Christopher B. Marshall² ; Fré ; dé ; rick Faucher¹ ; Maya Bar-Dolev³ ; Ido Braslavsky³ ; Robert L. Campbell¹ ; Virginia K. Walker¹ ; ⁴ ; Peter L. Davies¹ ; ^{peter.davies@queensu.ca}
• 关键词：LpIBP ; Lolium perenne ice-binding protein ; AFP ; antifreeze protein ; TH ; thermal hysteresis ; IRI ; ice recrystallization inhibition ; IBP ; ice-binding protein ; IBS ; ice-binding site ; CfAFP ; Choristoneura fumiferana antifreeze protein ; TmAFP ; Tenebrio molitor
• 刊名：Journal of Molecular Biology
• 出版年：2012
• 期刊代码：102_00222836
• 类别：imm
• 出版时间：9 March, 2012
• 卷：416
• 期：5
• 页码：713-724
• 文件大小：1396 K

摘要

The grass Lolium perenne produces an ice-binding protein (LpIBP) that helps this perennial tolerate freezing by inhibiting the recrystallization of ice. Ice-binding proteins (IBPs) are also produced by freeze-avoiding organisms to halt the growth of ice and are better known as antifreeze proteins (AFPs). To examine the structural basis for the different roles of these two IBP types, we have solved the first crystal structure of a plant IBP. The 118-residue LpIBP folds as a novel left-handed beta-roll with eight 14- or 15-residue coils and is stabilized by a small hydrophobic core and two internal Asn ladders. The ice-binding site (IBS) is formed by a flat beta-sheet on one surface of the beta-roll. We show that LpIBP binds to both the basal and primary-prism planes of ice, which is the hallmark of hyperactive AFPs. However, the antifreeze activity of LpIBP is less than 10%of that measured for those hyperactive AFPs with convergently evolved beta-solenoid structures. Whereas these hyperactive AFPs have two rows of aligned Thr residues on their IBS, the equivalent arrays in LpIBP are populated by a mixture of Thr, Ser and Val with several side-chain conformations. Substitution of Ser or Val for Thr on the IBS of a hyperactive AFP reduced its antifreeze activity. LpIBP may have evolved an IBS that has low antifreeze activity to avoid damage from rapid ice growth that occurs when temperatures exceed the capacity of AFPs to block ice growth while retaining the ability to inhibit ice recrystallization.