Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada.
Science. 2014 Feb 14;343(6172):795-8. doi: 10.1126/science.1247407.
When polypeptide chains fold into a protein, hydrophobic groups are compacted in the center with exclusion of water. We report the crystal structure of an alanine-rich antifreeze protein that retains ~400 waters in its core. The putative ice-binding residues of this dimeric, four-helix bundle protein point inwards and coordinate the interior waters into two intersecting polypentagonal networks. The bundle makes minimal protein contacts between helices, but is stabilized by anchoring to the semi-clathrate water monolayers through backbone carbonyl groups in the protein interior. The ordered waters extend outwards to the protein surface and likely are involved in ice binding. This protein fold supports both the anchored-clathrate water mechanism of antifreeze protein adsorption to ice and the water-expulsion mechanism of protein folding.
当多肽链折叠成蛋白质时，疏水区被压缩在中心，排斥水的存在。我们报告了一种富含丙氨酸的抗冻蛋白的晶体结构，该蛋白在其核心中保留了约 400 个水分子。这种二聚体、四螺旋束蛋白的假定冰结合残基向内指向，并将内部水分子配位成两个相交的多戊糖网络。该束在螺旋之间形成最小的蛋白质接触，但通过蛋白质内部的骨架羰基锚定在半笼状水单层上而稳定。有序的水分子向外延伸到蛋白质表面，可能参与冰结合。这种蛋白质折叠既支持抗冻蛋白吸附到冰上的锚定-笼状水机制，也支持蛋白质折叠的水驱逐机制。
