Mimicry of ice structure by surface hydroxyls and water of a β-helix antifreeze protein
Mimicry of ice structure by surface hydroxyls and water of a β-helix antifreeze protein
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DOI：
10.1038/35018604
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发表时间：
2000-07-20
期刊：
影响因子：
64.8
通讯作者：
Jia, ZC
中科院分区：
文献类型：
--
作者：
Liou, YC;Tocilj, A;Jia, ZC
昆虫抗冻蛋白（AFP）比鱼类AFP更有效地通过冰生长抑制降低溶液冰点（1，2）。来自黄粉虫的甲胎蛋白是一种小蛋白（8.4 kDa），由串联的12个残基重复序列（3）（TCTxSxxCxxAx）组成。在这里，我们报告了它的1.4埃分辨率晶体结构，表明这种重复序列转化为异常规则的β-螺旋。不仅12个氨基酸的环在主链上几乎相同，而且保守的侧链也位于基本相同的方向，使AFP可能是迄今为止观察到的最规则的蛋白质结构。该蛋白质几乎没有疏水性核心，但通过许多二硫键和氢键稳定。在蛋白质的保守侧，苏氨酸-半胱氨酸-苏氨酸基序排列形成平坦的β-折叠，即推定的冰结合表面。苏氨酸侧链具有完全相同的旋转异构体构象，并且OH基团之间的间距与冰晶格近乎完美匹配。与紧密结合的共面外部水一起，三排氧原子形成了一个二维阵列，模仿了冰层。
Insect antifreeze proteins (AFP) are much more effective than fish AFPs at depressing solution freezing points by ice-growth inhibition(1,2). AFP from the beetle Tenebrio molitor is a small protein (8.4 kDa) composed of tandem 12-residue repeats(3) (TCTxSxxCxxAx). Here we report its 1.4-Angstrom resolution crystal structure, showing that this repetitive sequence translates into an exceptionally regular beta-helix. Not only are the 12-amino-acid loops almost identical in the backbone, but also the conserved side chains are positioned in essentially identical orientations, making this AFP perhaps the most regular protein structure yet observed. The protein has almost no hydrophobic core but is stabilized by numerous disulphide and hydrogen bonds. On the conserved side of the protein, threonine-cysteine-threonine motifs are arrayed to form a flat beta-sheet, the putative ice-binding surface. The threonine side chains have exactly the same rotameric conformation and the spacing between OH groups is a near-perfect match to the ice lattice. Together with tightly bound co-planar external water, three ranks of oxygen atoms form a two-dimensional array, mimicking an ice section.