Effect of type III antifreeze protein dilution and mutation on the growth inhibition of ice
Effect of type III antifreeze protein dilution and mutation on the growth inhibition of ice
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DOI：
10.1016/s0006-3495(96)79476-6
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发表时间：
1996-11-01
影响因子：
3.4
通讯作者：
Davies, PL
中科院分区：
文献类型：
--
作者：
DeLuca, CI;Chao, H;Davies, PL
III型抗冻蛋白(AFP)冰结合部位残基的突变不仅降低了抗冻活性(表明未能阻止冰晶生长)，还改变了冰晶的形态，形成了拉长的六角双金字塔。一般而言，随着突变的严重程度，冰晶的c轴与a轴的比率从相似的2增加到10以上。在冰晶生长过程中，野生型甲胎蛋白连续稀释后，它也会增加。这与α-螺旋I型AFP的行为形成鲜明对比，在AFP中，冰结合残基的稀释或突变都不会使冰晶的c：a轴比高于标准的3.3。我们认为，III型AFP及其突变体产生的冰晶形态可以通过蛋白质与冰的棱柱面结合并通过阶梯生长抑制来解释。在这个模型中，AFP对冰的亲和力的降低导致棱镜表面单个台阶的填充，导致冰晶以更长的c：a轴比生长。
Mutation of residues at the ice-binding site of type III antifreeze protein (AFP) not only reduced antifreeze activity as indicated by the failure to halt ice crystal growth, also altered ice crystal morphology to produce elongated hexagonal bipyramids. In general, the c axis to a axis ratio of the ice crystal increased from similar to 2 to over 10 with the severity of the mutation. It also increased during ice crystal growth upon serial dilution of the wild-type AFP. This is in marked contrast to the behavior of the alpha-helical type I AFPs, where neither dilution nor mutation of ice-binding residues increases the c:a axial ratio of the ice crystal above the standard 3.3. We suggest that the ice crystal morphology produced by type III AFP and its mutants can be accounted for by the protein binding to the prism faces of ice and operating by step growth inhibition. In this model a decrease in the affinity of the AFP for ice leads to filling in of individual steps at the prism surfaces, causing the ice crystals to grow with a longer c:a axial ratio.